Preheat the oven to 400 degrees F (205 degrees C).
Line the muffin tin(s) with non-stick liners.
In a large bowl, combine the cornmeal, flour, brown sugar, baking powder, and salt.
Make a well in the center of the dry mixture. Add the buttermilk, sour cream, egg, egg yolk, and honey. Use a fork to lightly mix the ingredients together. Switch to a rubber spatula to fold the wet ingredients into the dry ingredients, stirring until just combined.
Melt the butter until browned then cool slightly and fold in the batter along with the diced jalapenos. Stir until just combined.
Divide the batter equally among the prepared muffin cups then top with a slice of jalapeno.
Bake until a cake tester inserted into the center of a muffin comes out clean, 8 to 10 minutes for the mini muffins and 15 minutes for the regular muffins. Place the pan on a cooling rack and let cool for 10 minutes.