Using two packs wipe 4 mushrooms with a damp paper towel; remove stems + scoop out gills; heat 1 tbsp oil in a skillet over med-high + cook mushrooms 2-3 min per side until browned + tender; add salt/pep + set aside

Form bison into 2; ¼-inch patties + season with salt/pep; heat 1 tbsp oil in skillet over med-high + cook 3-4 min per side; then rest 2-3 min (meat keeps cooking after taken off heat; do not overcook for best results)

Divide 2 tbsp guac + 2 tbsp salsa to mushroom buns; add burgers then close the lid