Preheat the oven to 375°F (190°C). Place a 9-inch cast-iron skillet in the oven while it heats so it’s nice and hot when you add the batter — this helps create a beautiful golden crust.
In a large mixing bowl, whisk together the cornmeal (1 cup), flour (1 cup), baking powder (1 tablespoon), salt (1/2 teaspoon), and sugar (1 tablespoon) until evenly combined.
In a separate medium bowl, whisk together the milk (1 cup), eggs (2), sour cream (1/2 cup), and oil (1/4 cup) until the mixture is smooth and creamy.
Pour the wet ingredients into the dry ingredients and stir gently just until combined — don’t overmix or the bread can turn dense. (The batter should be thick, creamy, and slightly lumpy — that’s exactly what you want. Those little lumps mean you haven’t overmixed, which keeps your cornbread tender and soft.)
Fold in the cheddar cheese (1 cup), Monterey Jack cheese (1/2 cup), green chiles (1 can), corn (1 cup), jalapeño, and green onions until evenly distributed.
Carefully remove the hot skillet from the oven and lightly grease it with oil or butter. Pour the batter into the skillet, spreading it evenly. You should hear a light sizzle as it hits the pan — that’s how you’ll know it’s perfect.
Bake for 30–35 minutes, or until the top is golden and a toothpick inserted in the center comes out clean.
Cool slightly before slicing. Serve warm with butter, a drizzle of honey, or alongside your favorite chili or soup.