​Make the sauce: mix together all the ingredients and set aside.

To make the fritters: Preheat oven to 250 degrees. Have a baking sheet with a wire rack ready.

Trim ends off zucchini and grate them on the large holes of a box grater, or use the shredding blade of a food processor. Remove the zucchini to colander.

Shred onion the same way and add it to the zucchini. Toss zucchini and onion with 1 teaspoon coarse salt and set aside over a bowl or in the sink for 10 minutes. Squeeze out much of the liquid using your hands or a clean dishtowel and add zucchini mixture to a large bowl. Add corn to bowl. Stir in egg, garlic, black pepper, flour, baking powder and shredded cheese.

Heat 2 tablespoons of oil in a large heavy skillet (cast-iron recommended) over medium-high heat. When oil is shimmering, drop scant 1/3 cupfuls of batter into the pan. Work in batches so not to crowd pan. You can press them down and shape them with a spoon before they set.

The corn will have a tendency to pop in the hot pan, so be careful! You may want to use a splatter guard to protect yourself.

Cook until the bottom is golden brown, about 3 to 4 minutes. If they darken too quickly, reduce the heat to medium. Flip the fritters and cook until browned on the other side, about 2 to 3 minutes more. Transfer fritters to baking sheet with a wire rack and then into the warm oven, until ready to serve. Repeat, keeping the pan well-oiled, with remaining batter.

Serve fritters warm, with a dollop of herb sour cream on top.