Over medium heat in a non-stick pan, melt a teaspoon of butter. Coat one side of each slice of bread with the melted butter and set aside. Add the remaining butter and canola oil to the pan. When butter is melted, saute the onion for 1 to 2 minutes, then add mushrooms and cook, covered, for 1 minute. Add seasonings and spinach, cover, and cook for 1 to 2 minutes, until spinach has wilted. Crack the egg into the pan and mix well with the vegetables. Shape to bread size. Place one slice of buttered bread, buttered side up, on the mixture and cover for 1 minute. When the vegetable/egg mixture is mostly cooked through, flip the sandwich so you're grilling the slice of bread. Add the cheese slice and the other slice of bread, butter side up. When the bottom side is grilled, fip to grill the other side. Makes one sandwich. Serve hot.