Blend the jalapeño, cilantro, green onions, oil, Greek yogurt, water, avocado, and salt in a food processor until the sauce reaches the desired consistency. Add a little more oil or water if needed for a smoother drizzle.

Pat the fish dry with paper towels and cut it into 2-3 inch pieces.

Place 1/2 cup flour in a shallow bowl. In another bowl, whisk together the remaining 1/2 cup flour, cornmeal, cornstarch, chili powder, baking powder, and salt.

Add the beer and beaten egg to the batter mixture and stir until combined.

Pour enough vegetable oil into a frying pan to partially cover the fish pieces and heat until a drop of water sizzles on the surface.

Coat each fish piece in the plain flour, then dip it into the batter before placing it in the hot oil.

Fry the fish for 3-5 minutes on each side until crisp and browned. Transfer to a paper towel-lined plate to drain excess oil, then sprinkle with salt while hot and allow to cool slightly.

Fill the tortillas with pieces of fried fish, cilantro, Cotija cheese, and jalapeño sauce before serving.