Combine all guacamole ingredients, mashing avocado slightly with a fork to create a creamy yet chunky consistency. Set aside.

Working with one bun at a time, open the sliced bun horizontally and lay face up on a cutting board or work surface. Spread each side of the bun with salsa, using one tablespoon per side.

Place half a slice of cheddar cheese on top of the salsa on each side of the bun. Spread two tablespoons guacamole on one side of the bun.

Top with four to five jalapeño rings and sprinkle with one teaspoon freshly chopped cilantro.

Fold over the bun to close the sandwich. Squeeze slightly to hold together, being careful not to allow any of the filling to ooze out. Continue assembling the sandwiches until all six buns are filled.

Dip each assembled sandwich gently into beaten egg and dredge in cornflake crumbs. (You may find this easier if you secure each bun with two toothpicks, but I had no trouble doing it without.)

Heat oil in a 12-inch (30-centimeter) frying pan over medium heat and fry buns about one to two minutes per side or until lightly golden. Make sure to fry them on all four sides to brown evenly. Fry only two buns at a time to prevent overcrowding.

Place fried buns on paper towels to drain and serve immediately. Serve with sour cream as an optional dipping sauce.