Step 1

Butter and flour a sheet of parchment paper, then place it on a tray (12 x 15 1/2 inches). With an electric hand mixer, cream 3 eggs with 1/2 cup of granulated sugar, the seeds scraped from the vanilla bean pod, and a pinch of salt, until you obtain a frothy mixture: this will take 10-15 minutes.

Step 2

Sift the flour and cocoa powder together; gently incorporate them into the egg mixture, then mix in the room temperature melted butter; distribute everything onto the tray, level it, and bake in a 350°F oven on the convection setting for 8 minutes.

Step 3

Dust a large sheet of parchment paper with powdered sugar; remove the cake from the oven, turn it over onto the parchment paper, and leave it under the tray so it cools gently and the humidity inside keeps it soft.

Step 4

Chop the black cherries. In a bowl, mix the milk, cream, 3 tablespoons of granulated sugar, the sour cream, and half of the black cherry syrup; pour everything into an ice cream maker and let it work for 30-40 minutes, until it reaches an ice cream consistency, adding in the chopped cherries after 15 minutes.

Step 5

In a bowl, mix the remaining black cherry syrup, 1 tablespoon of Alchermes liqueur, and 2 tablespoons of water.

Step 6

Cut the cake into 3 rectangles the same size as the walls of a long equilateral triangular baking mold (11 inches long, 2 3/4-inch sides, 2 1/2-inch height); if you are using a rectangular loaf pan, cut it into 4 rectangles: 2 the size of the long walls and 2 the size of bottom. Brush the rectangles with the liqueur mixture and use them to line the walls (and the bottom if you're using a rectangular loaf pan); fill with the ice cream, close with the last rectangle of cake, and place in the freezer for at least 1 hour.

Step 7

Beat the egg whites to stiff peaks; then, continuing to beat, add in the rest of the granulated sugar a little at a time. Turn the mold over onto a tray lined with parchment paper to remove the triangle; use a pastry bag to cover it with the beaten egg whites. In an oven set to the maximum temperature, bake the cake for 30-40 seconds, until the egg whites are golden and smell sweet.