for the salmorejo salsa:
1 pound plum tomatoes
1 white onion
3 garlic cloves
1/2 cup fresh lime juice
1/4 cup fresh cilantro, finely minced
1 tablespoon serrano pepper, de-seeded and finely minced
1 teaspoon kosher salt, plus more to taste
for the queso:
2 tablespoons unsalted butter
2 1/2 tablespoons all-purpose flour
2 cups whole milk, warmed
1 cup grated cheddar cheese
1 cup grated Monterey Jack cheese
1 1/2 teaspoon cornstarch
1 teaspoon kosher salt, plus more as needed
1. First, make the salsa. Slice the tomatoes in half through the stem end. Working with one tomato half at a time, use the large holes of a box grater to grate the cut side of the tomato into a bowl, stopping once you reach the skin. Discard the skin.
2. Grate the onion into the same bowl in the same manner, stopping once you reach the root end. Grate the garlic cloves into the same bowl. Add the lime juice, cilantro, serrano, and salt to the bowl and stir to combine. Taste and add more salt if needed.
3. Next, make the queso. Melt the butter in a heavy saucepan over medium heat. Add the flour and cook, stirring constantly, until the flour is thoroughly incorporated, approximately 1 to 2 minutes.
4. Whisking constantly to prevent any lumps from forming, slowly add the milk. Once all the milk has been added, continue to cook, stirring occasionally, until the mixture comes to a boil. Immediately reduce the heat to low and slowly add the cheddar and Monterey Jack cheeses, one handful at a time and stirring after each addition, waiting until the cheese is completely melted before adding more cheese.
5. Once all the cheese has been added, stir in the salt. Taste and season with more salt if necessary. Pour the queso through a fine-mesh sieve set over a clean bowl.
6. Serve the queso with the salmorejo salsa, chopped avocado, finely diced onion, Mexican crema, and a bowl of tortilla chips. Add crumbled cooked chorizo if desired.