Line a large baking sheet with parchment paper and set aside.
Slice bolillo bread rolls in half lengthwise. Spread 1/2 tablespoon of butter on each slice.
Place rolls on prepared baking sheet buttered side up and put in oven on the middle rack.
Broil for 2-3 minutes, until lightly toasted.
Remove from oven and top each slice with a layer of 1/4 cup refried beans and 1/4 cup shredded cheese.
Place molletes in oven one more time and broil for 3-4 minutes, until cheese has melted and is bubbly. Make sure to keep an eye on it during this time as the bread can quickly start to burn.
Top each slice with 2 tablespoons of pico de gallo. Serve immediately.
Notes
Instead of shredded Monterey Jack cheese, you can use any other melty cheese you have on hand. A classic Mexican melty cheese that's often used is Chihuahua cheese, or you could also use Mozzarella.
Can't find bolillo bread rolls? You can use any French bread, Italian bread, or sub sandwich bread instead.
Instead of traditional refried beans made with pinto beans, you could use refried black beans.
Adding butter or margarine is completely optional. Feel free to leave that out if you prefer.
To make the molletes a bit more filling, you could also add some sliced avocados, guacamole or even crumbled chorizo on top!