Preheat your oven to 350°F (175°C) and line baking sheets with parchment paper. In a bowl, sift together flour, baking powder, and salt. Cream together butter, powdered sugar, and granulated sugar until light and fluffy. Add sourdough discard, egg, and vanilla, mixing well. Fold in dry ingredients until just combined. Scoop onto prepared sheets and bake for 12-15 minutes until golden, then cool completely.

In a non-stick skillet, melt 2 tablespoons of butter over medium heat. Add sliced bananas, brown sugar, and cinnamon; sauté for about 8 minutes until caramelized. Blend about two-thirds of the mixture until smooth, reserving the rest.

Combine sweetened condensed milk, banana puree, vanilla extract, and a pinch of salt in a mixing bowl. In another bowl, beat cream cheese, then add heavy cream and whip until stiff peaks. Fold whipped cream into the banana mixture; optionally mix in crushed sourdough wafers.

Layer the ice cream mixture in a lined loaf pan with layers of reserved caramelized bananas and crushed wafers. Repeat layers, creating a swirled pattern. Cover and freeze for at least 6 hours.

Whisk together brown butter with maple syrup, cinnamon, and salt for the sauce. Beat heavy cream with maple syrup and vanilla until fluffy for the topping. Let the ice cream sit at room temperature for 10-15 minutes, serve topped with whipped cream and a drizzle of warm sauce.