Preparation Put oven rack in middle position and preheat oven to 350°F. Beat cream with an electric mixer until it just holds stiff peaks. Reduce speed to low and beat in dulce de leche, banana, and lime juice until combined. Freeze until firm but not frozen hard, at least 45 minutes. Brush tortillas with butter on both sides. Spread out on a baking sheet and toast, turning over once, until golden, 12 to 16 minutes. Cool tortillas completely, about 20 minutes. Divide cream mixture between 2 tortillas and top with remaining 2 tortillas. Freeze on baking sheet, loosely covered with foil, until frozen, about 1 hour.
Preparation Put oven rack in middle position and preheat oven to 350°F. Beat cream with an electric mixer until it just holds stiff peaks. Reduce speed to low and beat in dulce de leche, banana, and lime juice until combined. Freeze until firm but not frozen hard, at least 45 minutes. Brush tortillas with butter on both sides. Spread out on a baking sheet and toast, turning over once, until golden, 12 to 16 minutes. Cool tortillas completely, about 20 minutes. Divide cream mixture between 2 tortillas and top with remaining 2 tortillas. Freeze on baking sheet, loosely covered with foil, until frozen, about 1 hour.