Over medium heat melt 2 tablespoons butter in a sauté pan. Place garlic and mushrooms in the pan and sauté for 7-10 minutes until lightly browned. Set aside and wipe pan out with a paper towel.

Add 1 tablespoon butter to the pan and add the onions. Cook the onions until they begin to brown and caramelize.

Spread one inside of each roll with a teaspoon or so of butter and the other side with yellow mustard.

Layer the Swiss cheese, mushroom slices, onions, peppers and pickles on the bottom half of each roll and then cover with the top half.

Place the veggie Cubans on a hot and heavily buttered griddle, grill, panini pan or pan. Press the tops of the sandwiches down firmly and hold for a minute or so and then do the same to the others. When the bottoms begin to brown in a couple of minutes, carefully flip them and press them again. The pressing will give them a nice crispy crust while keeping the inside soft.

Remove from heat, cut in half and serve.