1 cup yellow stone-ground cornmeal
1/3 cup all-purpose flour
1 teaspoon baking powder
1/4 teaspoon baking soda
1 teaspoon kosher salt (Diamond Crystal)
1 pound very ripe plantains with black peel (about 2 medium)
1/2 cup thinly sliced scallions
1 teaspoon finely grated garlic
1 tablespoon finely grated scrubbed fresh ginger
1 Scotch bonnet pepper, minced with seeds, or 1 teaspoon red-pepper flakes
1/3 cup sour cream
Neutral oil, such as vegetable or grapeseed, for frying (about 4 cups)
½ cup mayonnaise
½ cup ketchup
1 tablespoon garlic powder
½ teaspoon granulated sugar
Kosher salt and black pepper
In a medium bowl, whisk together the cornmeal, flour, baking powder, baking soda and salt.
Cut off the ends of each plantain. Use a sharp knife to slice the peel along the length of each plantain without cutting into the flesh. Remove peels and discard. Slice plantains crosswise into 1-inch pieces. Using a mortar and pestle or a food processor, pound or pulse the plantains into a coarse purée. Avoid making the purée too smooth, especially if using a food processor.
Set aside 1/4 cup scallions for garnish. Stir or pulse the remaining 1/4 cup scallions, the garlic, ginger and Scotch bonnet pepper into the purée in the mortar or processor. Add the purée to the cornmeal mixture, and stir until the batter is just combined and resembles a shaggy dough. Fold in the sour cream.
Line a sheet pan with paper towels or set a wire rack in the pan. Heat 1 1/2 inches of oil in a medium saucepan or deep skillet over medium-high to 325 degrees. If you don’t have a deep-fry thermometer, test the oil temperature by lowering a pea-size drop of batter into the oil. Bubbles should form around the batter, and the drop should float to the surface.
Working in batches to avoid crowding the pan, use a small dessert spoon to drop heaping teaspoon-size portions of the batter into the hot oil and fry, turning frequently, until golden brown, about 5 minutes. The batter should not darken too quickly or take too long to cook through, so maintain the oil temperature by raising or lowering the heat as needed. Transfer the mosas to the paper towels or rack using a slotted spoon or tongs. Repeat with the remaining batter.
Serve warm, garnished with the remaining scallions, with fry sauce alongside.
In a small bowl, whisk together the mayonnaise, ketchup, garlic powder and sugar until smooth. Season generously with salt and pepper.
Use immediately or refrigerate in an airtight container for up to 1 week. This tastes great with tostones, French fries, slathered on a burger or even inside a grilled cheese.