Ingredients
1 cup corn oil
1 large yellow onion, finely diced
1½ teaspoons fine sea salt
1 cup corn kernels (canned or fresh)
8 large eggs, whites and yolks separated
4 cups/566 grams precooked yellow cornmeal (preferably P.A.N.)
4 cups whole milk
2 1/4 cups/8 ounces grated Muenster or mozzarella
Directions
1
Heat the oven to 375 degrees. Using a little bit of the oil, grease a 9-by-13-inch baking pan.
2
In a medium skillet over medium heat, add the oil and onion and cook, stirring occasionally, until translucent, 10 to 15 minutes. Remove from heat, stir in the salt and let the onions cool down for 5 to 10 minutes.
3
While that cools, transfer the corn kernels to a blender and blend them into a coarse purée, scraping down the side of the blender as needed; set aside.
4
In a stand mixer (or large bowl), beat the egg whites on medium-high with the whisk attachment until they are light, frothy and uniformly white, about 2 minutes (or 3 to 4 minutes if whisking by hand). They should at least triple in volume. Next, whisk in the yolks, one at a time; set aside.
5
In a very large bowl, combine the cornmeal and the puréed corn, mixing by hand with a rubber spatula until well incorporated. Then add the cooked onion with all of the corn oil and mix again until no dry streaks remain. Stir in about half the milk. Next, add all of the cheese and about half of the egg mixture and fold until combined, pulling the wet mixture from the edges into the center. Add the rest of the egg mixture and milk and fold until fully combined. (The mixture will look wet, similar to a cake batter.) Transfer to the baking pan.
6
Bake for 40 to 45 minutes, until the top is golden brown. (If you place a toothpick or knife through the center, it should come out clean.) Let it cool for 15 to 20 minutes before serving. (The sopa is best enjoyed while still warm. It will firm up as it rests.) The sopa will keep, covered tightly in aluminum foil, in the refrigerator for up to 4 days, or frozen for up to one month.