-
1
Collect the pig's blood fresh and stir it immediately and continuously to break up the fibrin threads before coagulation sets. Pass it through a fine chinois into a clean bowl and hold it at room temperature. Strained blood is fluid and a deep, even burgundy with no visible clots.
-
2
Melt the lard in a wide, heavy pan over the lowest possible heat. Add the sliced onions and sweat, stirring occasionally, for 45–60 minutes until deeply caramelised and reduced to a soft, mahogany mass. They are done when no sharp onion smell remains and a spoon dragged across the pan leaves a clean line.
-
3
Add the diced pork back fat to the caramelised onions and render gently until the fat cubes are translucent and yield to light pressure — opaque white centres signal underrendering. Remove from heat and allow the mixture to cool to 40–45°C; verify with a probe thermometer.
-
4
This is where the dish lives or dies. With the fat-and-onion mixture confirmed at 40–45°C — below the coagulation threshold of 65°C at which haemoglobin denatures — pour the strained blood and the cream into the pan in a steady stream, stirring constantly. Add the sea salt, quatre-épices, and cinnamon. The mixture must remain warm and fluid, a uniformly dark, glossy slurry; any grey granulation signals premature coagulation and the batch cannot be recovered.
-
5
Fit the rinsed hog casings onto a sausage funnel and fill loosely, leaving perceptible slack so the proteins have room to expand during poaching. Tie at 20-cm intervals. Prick any visible air bubbles with a sterile pin. The casing should feel soft and yielding, not taut, under the fingertips.
-
6
Bring a large pot of water to exactly 80°C and maintain it throughout poaching — a thermometer clipped to the side of the pot is essential. Lower the boudins in gently and poach for 20–25 minutes. The water must remain still and barely trembling; any rolling boil will burst the casings. The boudins are done when an instant-read probe inserted at the thickest point reads 72°C.
-
7
Transfer the poached boudins immediately to ice water and hold until fully cold. The gel matrix sets as the blood proteins cool; the sausage should feel firm and resilient under a finger, not soft or yielding.
-
8
To serve, heat butter in a heavy pan until it foams and begins to colour to a hazelnut brown. Sear the boudins over moderate heat for 2 minutes per side. The casing should take on a deep mahogany colour with audible sizzling; the surface firms and crisps without splitting. In a separate pan, sauté the apple slices in butter until golden and just tender. Serve alongside pommes purée.