01 -
Preheat oven to 175°C.
02 -
In a 20x20 cm or 23x23 cm glass baking dish, add unsalted butter and melt using a microwave. Coat the sides and base evenly with the melted butter to prevent sticking.
03 -
Add drained whole kernel corn and undrained creamed corn to the pan with the melted butter.
04 -
Add sour cream, granulated sugar, and kosher salt to the mixture in the pan.
05 -
Add packaged corn muffin mix to the pan. Using a spatula, stir thoroughly until ingredients are fully combined. Scrape down the edges to ensure an even mixture.
06 -
Transfer dish to the preheated oven and bake for 35 to 40 minutes, until the edges are golden brown and pulling away from the sides. The center should be set and no longer jiggle excessively; a toothpick inserted should come out clean.
07 -
Allow casserole to cool on a wire rack for several minutes. Serve warm.