In a pan on medium heat, add a touch of oil and cook your mushroom slices and pepperoni for about 2 minutes.
In a small pinch bowl combine your garlic powder, dried oregano and nutritional yeast.
Butter one side of each of the slices of bread and sprinkle on the garlic mixture evenly. On the other side of the slices spread your tomato sauce evenly.
One the side with the tomato sauce layer your fillings; first cheese slice, mushrooms, pepperoni, jalapenos and your second slice of cheese. Plce your second slice of bread, tomato sauce side down, on top of the filling and place in a pan on medium heat to cook and melt the cheese. In order to help the cheese melt be sure to place a lid over top of your pan. The bread should be golden brown on both sides and the cheese melted.