Preheat oven to 375°F (190°C). Line crust with parchment and fill with pie weights. Bake for 12-15 minutes, until the edges are set and lightly golden. Remove weights and parchment; bake 5–7 minutes more, until bottom is dry and pale golden. Let cool slightly.
Reduce oven temperature to 350°F (175°C). In a large bowl, mix coconut, pecans, graham crumbs, sugar, salt, and vanilla. Add egg whites and stir until fully combined. Pour filling into the blind-baked crust and smooth the top. Bake for 35–45 minutes, until the top is golden brown and the center is just set. Cool to room temperature, then chill for at least 2 hours for the cleanest slices.
Using a stand mixer or electric hand mixer, whip the heavy cream with powdered sugar and vanilla until medium-stiff peaks form. Spread a thin layer of dulce de leche over the chilled pie, if using. Top with banana slices and whipped cream.