Heat oil in a medium Dutch oven or other heavy pot over medium. Add onions and cook, stirring, until just beginning to turn golden brown, 10–14 minutes. Stir in beans and add bay leaf. Cook, stirring occasionally, until beans begin to soften and fall apart, 9–11 minutes. Season beans with salt and remove from heat. Remove and discard bay leaf. Mash beans with a potato masher until smooth and spreadable.
 
```ad-tip
title: **Do Ahead:**
Beans can be made 3 days ahead. Let cool; cover and chill.
```
 
#### PICO DE GALLO
##### Step 1
Toss tomato, red onion, cilantro, jalapeño, and lime juice in a small bowl to combine; season with salt.
 
#### EGGS AND ASSEMBLY
##### Step 1
Heat broiler. Generously butter cut sides of rolls and place, buttered side up, on a rimmed baking sheet. Broil until butter is melted, about 1 minute. Remove from broiler; spread ⅓ cup refried beans over cut side of each roll half and arrange cheese down center. Broil until cheese is melted and beginning to brown, about 2 minutes.
 
##### Step 2
Top each mollete with a fried egg, then pico de gallo, avocado, and pickled onion. Serve with hot sauce.