Add the beans to a large bowl and fill with water. Let them soak overnight so they absorb most of the water.

Drain the water from the beans and transfer them to a large pot. Add enough water to cover the beans and place on high heat.

Bring to a boil. Scum will float to the top—skim it off, then drain the beans. Refill the pot with fresh water, covering the beans again.

Boil on medium-high heat for 40-60 minutes. Once the beans are soft enough to crush between your fingers, drain the water.

Add the powdered sweetener and stevia to the pot with the beans. Stir continuously while cooking for 10 minutes. Use a spatula to mash the beans as they cook.

For a chunky paste, leave it as is. For a smooth texture, blend the mixture in a food processor or use a hand mixer until creamy.