Cook bacon in a 10-inch cast iron skillet over medium-high heat, stirring occasionally, until almost crisp and fat rendered, 7 to 8 minutes.

Set an oven rack about 6 inches from the heat source and preheat the oven’s broiler.

Thoroughly drain thawed corn in a colander. Add 1/2 corn to the skillet with bacon; cook and stir until kernels just start to turn golden brown, 3 to 5 minutes. Add green onions, jalapeños, and garlic; cook until vegetables start to soften and sweeten, 3 to 4 minutes. Tilt skillet; drain off some fat, using a paper towel to soak it up.

Season vegetables with salt, black pepper, and cayenne pepper; stir in cream and bring to a boil. Stir in remaining 1/2 corn; cook until heated through. Off heat, stir in about 2/3 each Monterey Jack and mozzarella cheeses to combine; top with remaining 1/3 each Monterey Jack and mozzarella cheeses and pinch cayenne pepper.

Broil in the preheated oven until heated through and top is browned, 5 to 10 minutes.