- Mix all dry sponge ingredients: flour, sugar, cocoa, salt, and baking powder. Add eggs, oil, and kefir. Incorporate with a mixer until just combined. Add red food coloring until desired hue is achieved.
- Transfer the batter into a prepared baking pan. Bake at 347F (175C) for about 45 minutes. Test doneness with a toothpick. Once baked, cool, wrap in plastic wrap, and refrigerate. (*Alternate option: Divide batter into three parts and bake in separate pans for 15-20 minutes.)
- For the berry confit, mix berries (without liquid if using frozen), 50g sugar, and cook on the stovetop. Mix remaining sugar with pectin. When the mixture boils, add the sugar-pectin mix and cook for a few minutes. Dissolve cornstarch in liquid, add to the berries, cook until thickened, and cool.
- For the cream, melt white chocolate with hot cream, mix, and cool. Add ricotta and mascarpone, whip until fluffy, and transfer to a piping bag.
- For the syrup, mix equal parts water and sugar, bring to a boil, and add berry-infused liqueur or strong alcohol. Cool.
Layer the cake, soaking each layer with syrup. Add a thin layer of cream, creating a cream border around the edges. Add berry confit in the center. Repeat layering process.