Set oven rack about 6 inches from the heat source and preheat the oven’s broiler. Line a baking sheet with aluminum foil. Place serrano peppers with cut sides down onto the prepared baking sheet.
Cook under the preheated broiler until the skin of the peppers has charred, 5 to 8 minutes. Immediately put peppers in a heatproof bowl, cover tightly with plastic wrap, and let sit until cool enough to handle, 5 to 10 minutes. Scrape the skins off with your fingers, core and seed chile peppers. Dice peppers.
Cut rib-eye steak into thin slices. Chop slices finely. Transfer to a bowl. Add serrano peppers, egg, panko, sriracha sauce, ginger, salt, pepper, and lime zest. Wet your hands and form mixture into ping pong-sized balls.
Coat a saute pan with olive oil and heat over medium-high heat. Add meatballs and sear both sides evenly, about 4 minutes. Pour in beer and soy sauce. Stir in peanut butter and reduce heat; simmer sauce until thickened, 5 to 10 minutes. Garnish with cilantro.