Place the cubed 2 lb pork shoulder cut into 1-inch cubes, ¾ lb veal shoulder cut into 1-inch cubes, and ¼ lb pork back fat cut into 1-inch cubes on a rimmed baking sheet or in a 1 onion sliced mixing bowl. Freeze for 20–30 minutes until very firm but not frozen solid. ⅓ cup heavy cream very cold meat grinds cleanly and keeps fat from smearing, which is key to a juicy sausage.

Combine all the ground mace blend ingredients in a mixing bowl (Small) and mix well. Set aside.

Working quickly to keep everything ⅓ cup heavy cream very cold, grind the chilled meat mixture through a meat grinder fitted with a medium die (about 1/4-inch plate). Grind it once through. If the meat feels ¼ cup ice water or the ¼ lb pork back fat cut into 1-inch cubes looks smeared, return it to the freezer for 10 minutes before continuing.

Transfer the 1 tsp white pepper freshly ground meat to a 1 onion sliced, chilled mixing bowl. Add the ½ tsp ground mace blend, cold ⅓ cup heavy cream very cold, and ¼ cup ice water. Mix vigorously by hand (or with a stand mixer on medium using the paddle attachment) for 2–3 minutes, until the mixture becomes sticky and cohesive — it should pull away from the bowl sides and hold its shape when pressed.

Cook a small test patty in a ¼ cup ice water frying pan for 2–3 minutes per side. Taste and adjust seasoning in the remaining mixture if needed — add more 1 ½ tsp kosher salt, 1 tsp white pepper freshly ground, or ½ tsp ground mace to your preference.

Drain the soaked 4 oz natural hog casings soaked in warm water for at least 30 minutes, rinsed inside and out casings and thread one end onto the sausage stuffer tube. Feed the entire casing onto the tube, leaving a few inches hanging off the end. Tie a knot at the open end.

Fill the sausage stuffer with the meat mixture and begin extruding slowly, guiding the 4 oz natural hog casings soaked in warm water for at least 30 minutes, rinsed inside and out with your non-dominant hand to keep the fill even and firm — but not too tight, or the sausages will burst during cooking. Fill the entire length of casing in one continuous coil.

Once filled, twist the coil into individual links about 5–6 inches long. Twist each link in alternating directions (forward, then back) to seal them. Tie off the last link with a knot. Use a sausage pricker or thin needle to prick any visible air pockets.

Place the linked sausages uncovered on a wire rack set over a baking sheet. Refrigerate for at least 1 hour (or overnight) to allow the casings to dry slightly and the flavors to meld. This step greatly improves the final texture and snap.

In a frying pan (Large) or saucepan, combine the 2 cups lager or German-style beer such as a pilsner or Märzen and sliced onion sliced over medium heat. Bring to a gentle simmer — do not boil. Add the bratwurst links and simmer (poach) for 10–12 minutes, turning once halfway through, until the internal temperature reaches 150°F. This ensures they're cooked through before the final sear.

Remove the bratwurst from the 2 cups lager or German-style beer such as a pilsner or Märzen bath and pat dry with paper towels. Discard the beer and 1 onion sliced or set aside if you'd like to serve sautéed onions alongside.

Wipe 4 oz natural hog casings soaked in warm water for at least 30 minutes, rinsed inside and out the frying pan and melt the 2 tbsp unsalted butter over medium-high heat until foaming. Add the bratwurst and sear for 3–4 minutes per side, turning every minute or so, until deeply golden 1 onion sliced on all sides. The internal temperature should reach 160°F.

Rest the bratwurst for 3–5 minutes before serving. Serve on a crusty roll with whole-grain mustard, sauerkraut, and the reserved 2 cups lager or German-style beer such as a pilsner or Märzen-braised 1 onion sliced.