Melt the white chocolate with the butter in a saucepan over low heat. Add the dulce de leche and stir until incorporated. Remove from the heat and set aside. Preheat the oven to 425 degrees F (220 degrees C). Using a stand or hand mixer, beat the eggs with the sugar until the mixture is pale and has doubled in volume. Gradually add the white chocolate mixture, and then the flour. Take your time to avoid lumps. Divide the batter among 6 ramekins. Bake until the cakes are golden brown and the centers are still soft, about 15 minutes. Sprinkle with sea salt and serve.