Add pinto beans to a large bowl and cover with cool water for at least 6 hours or overnight uncovered at room temperature.

Once beans are soaked, drain and set aside.

Chop onion into slices and cut serrano and chipotle pepper into strips.

In a stockpot, transfer the soaked beans with garlic, epazote, and cold water.

Place this mixture over medium heat for two hours.

Meanwhile, in a large skillet, add lard to melt over medium heat.

Add chopped onions and salt. Cook until they turn brown for 15 minutes.

Once done, add serrano pepper and chipotle powder, cook it for another one minute.