Place the bison tenderloin in the freezer for 15–20 minutes until very cold but not frozen solid; this firms the meat and makes it easier to finely dice. Using a sharp knife, trim any sinew or fat and then cut the meat into very small dice (about 1/8" to 1/4"). Aim for uniform pieces for a good texture.

Mix aromatics and seasoning

In a mixing bowl combine the minced shallot, chopped capers, Dijon mustard, Worcestershire sauce, olive oil, finely chopped parsley, lemon zest, salt, and black pepper. Stir until combined.

Combine egg yolk and meat

Add the egg yolk to the seasoning mixture and whisk lightly to create a cohesive dressing. Add the diced bison and gently fold with a spoon or rubber spatula until the meat is evenly coated. Taste and adjust seasoning with additional salt, pepper or a squeeze of lemon if desired. Keep chilled until plating.

Accompaniments

Grill/toast bread

Heat a grill pan or skillet over medium-high. Butter one side of each bread slice lightly. Grill or toast bread, buttered side down, until golden brown and slightly crisp, about 1–2 minutes per side on a hot pan (or 3–4 minutes under a broiler), taking care not to char aggressively. Keep warm.

Assemble and garnish

On chilled plates, portion the tartare into 4 equal servings (see servings). Arrange the shaved Manchego alongside or draped over the tartare. Place 2–3 slices of grilled bread per plate. Garnish with a few extra capers and a small scatter of microgreens or arugula. Serve immediately so the bread remains crisp.