Season each steak with salt and pepper on each side. In a skillet over high heat (“screaming hot pan”), sear each steak for 10-15 seconds per side. Only sear long enough to form a light crust. Do not overcook – the centers should be raw. Set aside to cool to room temperature. Begin thawing the puff pastry on a cutting board.

Reduce the temperature of the pan to medium and deglaze the bottom of the pan with the white wine, scraping up the browned bits on the bottom of the skillet. When most of the liquid has cooked off, toss in the chopped prosciutto and cook until most of the fat has melted and the prosciutto is just starting to crisp up.

Stir in the shallot, mushrooms, and whole-grain mustard. Add splashes of white wine as needed if the pan gets too dry. Continue to cook until the shallots and mushrooms are tender and softened, about 10-15 minutes. Remove from the skillet and set aside to cool to room temperature.

Open the thawing puff pastry to allow it to thaw more quickly while the duxelles mixture cools. When the puff pastry is pliable, cut it down the seams then across to make 12 squares from each sheet of puff pastry. Place any puff pastry not being used back into the fridge to chill.

Preheat the oven to 450°F. Cut each bison steak into 4-6 small bite-sized pieces. Grease a muffin pan generously with cooking oil. Press a square of puff pastry into each cup, leaving the corners pointing upwards. Place a single piece of bison steak into each cup then place about one tablespoon of the duxelles mixture on top.

Brush any exposed edges of puff pastry with egg wash then transfer to the oven to bake for 5-8 minutes – until the puff pastry is golden brown and puffed up. Cool for 10 minutes prior to serving. Garnish with a sprinkling of fresh thyme and enjoy!