Beef Stroganoff in Black Truffle Pasta

STEP 1: MAKE THE TRUFFLE PASTA DOUGH (AND REST)
Mound the flour and salt on a clean work surface and make a well in the centre. Crack in the whole egg and three yolks, add the olive oil and the truffle paste. If you have a fresh truffle, grate a small piece directly into the well — the dough will be flecked black through the sheet. Whisk the wet ingredients with a fork, slowly drawing in flour from the edge of the well until you have a shaggy mass. Knead by hand for 8–10 minutes until smooth, supple, and just tacky — it should spring back slowly when pressed with a finger. Wrap tightly in cling film and rest at room temperature for at least 30 minutes (an hour is better). Resting hydrates the gluten and relaxes it so the sheet rolls thin without tearing or springing back.

STEP 2: BUILD THE STROGANOFF FILLING
Pat the diced tenderloin dry and season with salt and a generous crack of pepper. Heat a heavy skillet over high heat until it just begins to smoke. Add the olive oil and 1 tablespoon of the butter; when the butter foams, add the beef in a single layer and sear hard for 60–90 seconds, tossing once, until deeply browned outside and rare in the middle. Lift the beef out onto a plate — it will finish cooking later inside the pasta. Reduce the heat to medium. Add the remaining butter, then the shallots, garlic, and chopped mushrooms; sauté 8–10 minutes until the mushrooms have given up their water and the mixture is dry and glossy. Stir in the Dijon. Pull the pan off the heat, pour in the cognac, and return to the heat to flame off (or simmer it dry). Add the stock and reduce to a thick glaze — you should be able to draw a line through it with a spoon. Off the heat, stir in the crème fraîche, Worcestershire, sherry vinegar, and parsley. Fold in the seared beef and its resting juices. Season decisively with salt and pepper. Spread the filling on a tray to cool quickly — it must be cold before it goes into pasta, or the dough will tear.

STEP 3: MAKE THE MUSHROOM VELOUTÉ
Strain the porcini through a fine sieve (/cooking-equipment/fine-mesh-sieve)lined with a coffee filter or paper towel and reserve the soaking liquor. Chop the porcini roughly. In a saucepan over medium-high heat, melt the butter and add the cremini, porcini, shallot, garlic, and thyme. Sauté hard for 8–10 minutes until everything is deeply caramelised — colour is flavour here. Deglaze with the white wine and reduce until almost dry. Add the stock and the reserved porcini liquor and simmer for 15 minutes. Add the cream, simmer another 2 minutes, then transfer to a blender (or use a stick blender) and blitz on high for a full minute until silky. Pass through a fine-mesh sieve back into a clean pan, pushing hard with a ladle. Season with salt, white pepper, and a few drops of lemon juice — the velouté should taste like concentrated forest, not like cream. Keep warm.

STEP 4: ROLL, FILL, AND CUT THE PASTA
Divide the rested dough into quarters; keep what you're not working with under a damp cloth. Flatten one piece into a rectangle and pass it through your pasta machine,(/cooking-equipment/electric-pasta-maker) starting at the widest setting and stepping down two settings at a time, folding the sheet in thirds (a letter fold) at the first two passes to laminate it. Continue rolling without folding until you reach the second-thinnest setting — the sheet should be just translucent enough to see your hand through. Lay the sheet on a lightly floured board and cut 2 1/2-inch (6cm) rounds with a cutter. On half the rounds, place a heaped teaspoon of cold filling slightly off-centre. Brush the exposed pasta border lightly with egg wash using a pastry brush, lay a second round on top, and press the air out from the filling outward to the edge. Seal firmly, then crimp with the tines of a fork or your fingers. Any air trapped inside will burst the pasta in the water. Lay finished pieces on a semolina-dusted tray. You should end up with 16–20 stuffed rounds. Cover with a clean towel until ready to cook.

STEP 5: COOK THE PASTA
Bring a wide pan of well-salted water to a steady gentle boil — not a rolling boil, which can split the seals. Slip the pasta in carefully and cook for 3–4 minutes; they will rise to the surface and the dough should be tender but still have the slightest chew where it overlaps. Lift them out with a slotted spoon, draining well.

STEP 6: PLATE
Warm shallow bowls. Ladle a generous pool of mushroom velouté into the centre of each bowl. Arrange 4–5 stuffed pasta on top of the velouté (do not submerge — you want the filled shapes to show). Shave fresh black truffle generously over the pasta with a truffle shaver or vegetable peeler,(/cooking-equipment/citrus-peeler) scatter chives, finish with a few drops of truffle oil and a pinch of Maldon sea salt. Serve immediately.