Easy Gluten Free Sweet Corn Spoon Bread

gluten free Jiffy-style corn muffin mix (1/2 recipe)

unsalted butter, melted and cooled

sour cream, at room temperature (can replace with plain Greek-style yogurt)

creamed corn (homemade creamed corn or canned), at room temperature

frozen corn kernels, defrosted

eggs (150 g, weighed out of shell) at room temperature (optional step: separating the eggs)