In your saute pan, add 1.5 tbsp butter along with the minced mushrooms, saute for 4-5 minutes until tender, season with salt and pepper. Set aside to cool. Repeat this step with the sliced mushrooms. Set aside. In a large bowl add the bison, steak seasoning, garlic powder, ground mustard, 1 tbsp of Worcestershire and a few dashes of salt and pepper. Using a spoon, mix until all ingredients are blended. Add the cooled minced mushrooms to the bison mixture and gently mix. (Try not to over mix) .