Peel and slice large onions into 1-inch thick rings and lay them flat on a wax paper-lined tray.

In a large mixing bowl, combine softened cream cheese, grated cheddar, diced jalapenos, garlic powder, salt, and black pepper, mixing thoroughly.

Fill each onion ring with the cheese mixture using a spoon, packing it level with the top.

Coat each filled onion ring in flour, dip into beaten eggs, and roll in panko crumbs.

Place the breaded onion rings on a baking sheet in a single layer and freeze for at least 3 hours.

Heat vegetable oil in a deep pan to 385°F and fry the frozen onion rings in batches until golden brown.

Transfer the fried onion rings to a paper towel-lined plate to drain excess oil and serve hot.