Preheat your oven to 400 degrees Fahrenheit.

Melt 1 tablespoon of butter in a skillet over medium heat.

Sautee sliced mushrooms until they release their liquid and most of it has evaporated.

Crumble in dried chile arbol (including seeds, but not the stem).

Sautee for another 1-2 minutes.

While the mushrooms are cooking, toast the bolillo roll halves in the preheated oven.

Spread 0.5 tablespoon of butter over each toasted bolillo half.

Top each bolillo half with 2 tablespoons of refried beans.

Add 1 ounce of sliced fresh mozzarella (or shredded melting cheese) to each.

Spoon the sauteed mushrooms onto the cheese.

Garnish with chopped scallions.

Return the bolillo roll halves to the oven.

Bake until the cheese is completely melted and the beans are hot.

If desired, broil briefly to brown the cheese, being careful not to burn the edges of the rolls.