Pat sweet potatoes with paper towels to absorb excess moisture. Transfer to large bowl.
Add corn, cheese, flour, serrano, cilantro, egg, pepper and salt. Mix well with your hands.
Heat a skillet over medium-high heat. Add the avocado oil and heat until it ripples.
Using a 2 tablespoon ice cream scoop, drop the batter into the skillet and flatten into a round pancake. Ensure fritters are at least 1/2-inch apart while frying.
Fry fritters until they are golden on both sides, about 4 minutes total, flipping halfway through.
Transfer to paper towels to drain. Serve warm.