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)

Add a handful of spinach to 2 mushroom buns with 1-2 tbsp guac; add burgers then close the lid