Preheat the oven to 350 degrees F. Melt the butter in a large skillet over medium-high heat. Add the pineapple and a pinch of salt; cook, turning the pineapple occasionally, until softened and browned in spots, 5 to 7 minutes. Reduce the heat to medium and stir in 1/4 cup Dulce de Leche. Cook until the pineapple is glazed, 2 to 3 more minutes. Remove from the heat; let cool slightly.
Place the rolls, cut-side up, on a baking sheet; bake until lightly toasted, about 3 minutes.
Beat the heavy cream, vanilla and a pinch of salt in a medium bowl with a mixer on medium speed until stiff peaks form, 1 to 2 minutes; fold in 2 tablespoons Dulce de Leche until just combined. Spread each roll half with about 1/2 tablespoon Dulce de Leche and top with the pineapple mixture. Top with ice cream, the whipped cream, Dulce de Leche and coconut.
Homemade Dulce de Leche:
Yield:Photograph by Con Poulos
Pour two 14-ounce cans sweetened condensed milk into a 9-by-13-inch baking dish. Cover with foil and set in a roasting pan; add enough hot water to come halfway up the sides of the dish. Bake at 425 degrees F until thick and dark amber, about 1 hour 15 minutes. Transfer to a food processor and puree until smooth. Refrigerate until thickened, 1 hour. (Makes about 2 cups.)
You can use jarred or canned dulce de leche (usually found near the dessert sauces) for this recipe, or make your own.