Place the bacon in a large skillet over medium heat and cook until crispy and the fat has rendered.
Remove the bacon from the skillet to a paper towel, then crumble it once cooled, ensuring you keep the rendered fat in the pan.
Add the sliced mushrooms, diced yellow onion, and shredded carrots to the skillet, sautéing them in the bacon fat until the vegetables are tender and golden.
Add the ground beef to the skillet, breaking it apart with a spatula as it browns.
Season the mixture with sea salt, black pepper, garlic powder, and fresh thyme, stirring well to combine the flavors.
Cook until the beef is fully browned and cooked through, then stir the crumbled bacon back into the mixture.
Slice the buckwheat biscuit in half and lightly toast it until the edges are warm and slightly crisp.
Spoon the savory beef and mushroom mixture onto the biscuit halves to create a sandwich and serve immediately.