Preheat the oven to 425 degrees F. Place two 7-stick cast-iron corn stick molds in the oven to heat at least 15 minutes. Melt 4 tablespoons butter in a medium saute pan over medium-high heat until it foams. Toss in the jalapeno, scallions and garlic. Saute until softened, 2 to 3 minutes. Season with a little salt. Set aside to cool slightly.
Combine the cornmeal, flour, sugar, baking soda and 1/2 teaspoon salt in a large bowl. Whisk the buttermilk and egg lightly in a small bowl until combined. Make a well in the center of the dry ingredients and pour in the buttermilk mixture all at once. Stir the two mixtures together just until combined. Add the jalapeno mixture to the bowl along with any butter in the pan. Add the cheddar cheese and stir to combine (the batter will be thick).
Remove the hot pans from the oven and brush with the remaining 2 tablespoons melted butter. Divide the batter among the molds, then place back into the oven and bake 10 to 12 minutes, until lightly golden and springy to the touch.