Preheat the oven to 400 F and line two 12-cup muffin tins with paper liners or coat with nonstick spray.

In a large bowl, whisk together the cornmeal, flour, sugar, baking powder and salt until evenly blended.

In a separate bowl, whisk the eggs, buttermilk and vegetable oil until smooth.

Pour the wet ingredients into the dry ingredients and stir with a spatula just until no dry streaks remain; a few lumps are fine and overmixing makes tough muffins.

Fold in the shredded cheddar and diced jalapenos, reserving a small handful of each to scatter on top.

Divide the batter evenly among the 24 muffin cups, filling each about three-quarters full.

Scatter the reserved cheese and jalapeno over the tops.

Bake for 16 to 18 minutes, rotating the pans halfway through, until the tops spring back when pressed lightly and a toothpick inserted in the center comes out clean.

Cool the muffins in the tins for 5 minutes, then transfer to a wire rack to cool for another 10 minutes before serving.