In a large mixing bowl, combine the chopped hard-boiled eggs, shredded mozzarella cheese, Kewpie mayonnaise, sriracha, minced chives, salt, and cracked black pepper. Gently fold together until well combined.

Preheat a non-stick skillet over medium-high heat for about 2-3 minutes. Lightly spray with olive oil cooking spray.

Using a 1/4 measuring cup, scoop out the egg salad mixture and drop it onto the skillet, forming small cakes. Cook for 1-2 minutes until the bottoms are golden brown; flip and cook for an additional minute.

Toast slices of gluten-free bread until golden and crispy, about 3-5 minutes.

Place cakes on the toasted bread, top with sliced avocado and jalapeño slices, and serve warm.