Tagliatelle al ragù

Method

1. Finely dice the onion, carrot and celery into pieces of about 4 mm and cut the pancetta into small cubes.
2. Heat the oil and butter in a wide heavy-based pot and let the pancetta render over medium heat for 3 minutes. Add the diced vegetables and sweat them, stirring often, for 10 minutes until soft and translucent; they should not brown.
3. Add the minced beef and pork, raise the heat and break the meat up into small crumbs with a wooden spoon. Cook for about 10 minutes until the released juices evaporate and the meat starts to colour lightly on the bottom.
4. Pour in 120 ml of wine and simmer, stirring now and then, for about 5 minutes until it has almost completely evaporated. Then add 150 ml of milk and simmer gently for another 10 minutes until the meat has absorbed it.
   TipWhy milk and cream curdleMilk proteins can take the heat and they can take a squeeze of lemon – just not both at once.Why and howShow less

   Why

   Most of the protein in milk (about 80 %) is casein, which floats around in tiny clusters called micelles; they are kept apart by an electric charge and, above all, by a protective layer of the protein κ-casein on their surface. Acid (lemon, wine, tomatoes) and salt weaken that protection, and heat speeds the whole process up considerably: boiling alone won't curdle milk, but together with acid or salt the clusters stick together and the sauce turns into flecks and whey – and the more of these at once, the faster it happens. High-fat cream (whipping cream, from roughly 25–30 % fat) contains little protein, and what there is gets spread over the surface of the fat droplets, so it usually survives a short boil even with acid. Milk, single or cooking cream, sour cream and yogurt have more protein, and the cultured ones are already acidic, so they curdle easily in a hot sauce. Starch from flour or potato starch slows the proteins' clumping – the swollen starch granules probably keep them apart – which is why a thickened sauce holds together better.

   How to do it

   1. Take sour cream, yogurt or milk out of the fridge 15–30 minutes in advance so they aren't ice-cold.
   2. Temper: stir a few spoonfuls of the hot sauce into the dairy first, then pour it into the pan.
   3. Once sour cream or yogurt is in, don't boil the sauce again – just heat it through.
   4. If the dairy has to simmer, mix it with a little flour or starch beforehand.
   5. Add salt and acidic ingredients (lemon, wine) at the end, tasting as you go.
   6. Where the recipe allows, use whipping cream – it is the most forgiving.

   If it goes wrong

   A curdled sauce made from fresh ingredients is edible, it just looks untidy; but if the milk curdled on its own or smells sour, it has gone off and belongs in the bin. Slight graininess can often be smoothed out with a stick blender. Large curds won't come back together – you can strain the sauce, but it won't be silky again; next time temper the dairy and don't boil the sauce after adding it.

   Full card

5. Stir in the tomato paste and the sieved tomatoes, add 3 g of salt and the pepper and bring to the boil. Turn the heat down to the lowest setting, cover with the lid slightly ajar and let the ragù barely bubble for 2.5 hours. Stir from time to time and add a splash of water whenever it starts to catch (about 300 ml in total). The finished ragù is thick and glossy with fat on the surface; adjust the salt.
   TipTomatoes, tomato paste and acidityTomatoes have character: raw paste is sharp and sour, but a few minutes in fat give it a rounded flavour.Why and howShow less

   Why

   Tomato paste is concentrated tomato flesh with plenty of sugars and acids; briefly fried in fat, some of the sugars brown and the raw, sharply sour taste turns full and rounded, but it must be stirred, because it scorches easily on a dry pan base. Long simmering, fat, cream or a little sugar soften a sharp sauce; sugar doesn't neutralise the acid, though, it only balances it on the palate. Baking soda really does neutralise acid, but in tests it made the sauce taste flat, and larger amounts foam and taste soapy, so a pinch at most. Acid firms up the cell walls of vegetables and pulses, so beans, chickpeas and potatoes soften more slowly in tomato sauce. Acidic food doesn't belong in uncoated aluminium: the German BfR advises against cooking or storing acidic and salty food, such as tomato purée, in uncoated aluminium pots, because aluminium migrates into it; with cast iron, manufacturers say long cooking of acidic food strips the protective seasoning.

   How to do it

   1. Stir the paste into hot fat and fry it for a few minutes, stirring constantly, until it darkens and smells sweet; then add liquid at once.
   2. Simmer a sour sauce for longer and round it off with fat or cream; add sugar little by little and taste.
   3. Use baking soda only as an exception, a pinch per pot at most, and let it fizz out before tasting.
   4. Cook beans, chickpeas and potatoes until tender first, or allow longer cooking in the sauce – see the Cooking pulses card.
   5. Cook and store tomato sauces in stainless steel, enamel or glass, not in uncoated aluminium or new, lightly seasoned cast iron.

   If it goes wrong

   Paste that has scorched on the base won't lose that taste: pour the sauce into a clean pot without scraping and start again with a fresh batch. An overly sour sauce is saved by longer simmering, a knob of butter or a spoonful of cream. Dilute a sauce that tastes soapy after soda with canned tomatoes and leave the soda out next time.

   Full card

6. Towards the end of the simmering, bring 3 litres of water with 20 g of salt to the boil, add the dried egg tagliatelle and cook them al dente according to the packet, usually 6–8 minutes. Fresh homemade tagliatelle (Fresh egg pasta recipe) need only 2–3 minutes. Drain the pasta.
   TipCooking pastaPasta water isn't waste, it's liquid glue that talks the sauce into clinging to the pasta.Why and howShow less

   Why

   In the first minutes of boiling, starch is released from the surface of the pasta and it turns sticky; plenty of rapidly boiling water and a stir at that point stop it clumping, and the water doesn't cool down as much when the pasta goes in. Salt only gets into pasta while it cooks, which is why the water is salted generously, roughly 10 g per litre; that amount has a negligible effect on the boiling point, and oil in the water is pointless because it floats on top and doesn't prevent sticking. The cooking water is full of dissolved starch that thickens the sauce and helps its fat combine with water into a smooth emulsion that clings to the pasta. That is why pasta isn't rinsed after draining – you would wash off the starch the sauce holds on to and cool the pasta down; the only exception is pasta for a cold salad.

   How to do it

   1. Allow roughly a litre of water per 100 g of pasta and add about 10 g of salt per litre once it boils.
   2. Drop the pasta into rapidly boiling water and stir now and then for the first two minutes.
   3. Don't add oil to the water; it won't stop sticking.
   4. Cook a minute or two less than the packet says and keep tasting.
   5. Before draining, scoop out a mugful of the cooking water.
   6. Don't rinse the pasta; transfer it straight into the sauce and finish cooking it there with a little of the cooking water.

   If it goes wrong

   Loosen pasta that has stuck together in the sauce with a little hot cooking water, or dip it briefly in boiling water and stir. Overcooked pasta won't firm up again – bake it or add it to a soup, and next time start tasting earlier. Under-salted pasta can only be rescued by a well-seasoned sauce.

   Full card

7. Tip the pasta into the pot with the ragù and toss over low heat for 1 minute so the sauce coats it evenly. Serve at once, sprinkled with grated Parmesan.