Melt the finely chopped dark chocolate over a double boiler until smooth and glossy, then set aside to cool slightly.
In a clean bowl, whisk the egg yolks with half of the sugar until thick and pale, and the mixture leaves a ribbon when drizzled from the whisk.
In another bowl, whip the egg whites until foamy, then gradually add remaining sugar, beating until stiff, glossy peaks form.
Gently fold the melted chocolate into the egg yolk mixture, then carefully fold in a spoonful of whipped egg whites to loosen the batter.
Gradually fold in the remaining egg whites, being careful not to deflate the batter, until smooth and homogeneous.
Sift the all-purpose flour, sea salt, and chili powder together, then gently fold into the batter until just combined.
Pour the batter evenly onto a parchment-lined baking sheet, smoothing the surface gently with a spatula.
Bake in a preheated oven at 350°F (175°C) for about 12-15 minutes, until the sponge is puffed, glossy, and slightly springs back when pressed.
Once baked, invert the sponge onto a clean kitchen towel or parchment paper and carefully remove the baking sheet, then let it cool slightly.
Spread the spiced caramel sauce evenly over the sponge, leaving a small border around the edges for rolling.
Starting from one end, gently roll up the sponge with the filling inside, pressing lightly to shape it into a tight log.
Whip the heavy cream until soft peaks form, then refrigerate until ready to serve or spread over the rolled cake for extra indulgence.
Garnish the top of the roll with a sprinkle of sea salt and a bit of chili powder for extra flair, then slice and enjoy your chocolate coastal roll.
