Step 1

Make the soup: In a large pot over medium heat, heat the oil until shimmering. Add the onion and cook, stirring frequently, until softened but not brown, 4 to 5 minutes.

Step 2

Add the garlic, cumin and achiote and cook, stirring, until aromatic, about 30 seconds. Add the potatoes and stir to coat. Add the chicken broth or water and salt, and bring to a boil. Reduce the heat to low, cover and simmer until the potatoes are very tender, about 20 minutes. Remove from the heat.

Step 3

Using a slotted spoon transfer about 1 cup of the potatoes to a cutting board and cut them into small pieces.

Step 4

Use an immersion blender to blend the soup in the pot until smooth. (Alternatively, let the soup cool, then puree in batches in a regular blender.) Return the soup to medium-low heat and warm through. Stir in the milk and cheese until the cheese is melted. Return the chopped potato to the pot and stir to combine. Taste, and season with additional salt as desired.

Step 5

To serve: Ladle the soup into bowls, garnish the avocados, cilantro, scallion, cheese and hot sauce, if using, and serve.