Chocolate roll "Herman"

Ingredients:

• 1 cup unsweetened condensed milk
• 2 and 1/4 cups granulated sugar
• 3 large egg yolks + 3 large eggs, room temperature
• 275g unsalted butter (110g cubed, 165g softened)
• 3 tsp vanilla extract
• 1 and 2/3 cups sweet coconut flakes, toasted
• 1 cup chopped pecans
• 1 and 1/4 cups premium flour
• 0.5 tsp of soda
• 0.5 tsp salt
• 1/4 cup unsweetened cocoa powder + extra for sprinkling
• 30 g dark chocolate, finely chopped
• 1/3 cup strong hot coffee
• 1/3 cup of sour milk or kefir
• Powdered sugar, for dusting

Preparation:

1. Position a rack in the middle of the oven and preheat the oven to 350°F (175°C). Lightly grease a 13x18-inch baking sheet; line it with parchment paper, allowing the parchment paper to extend about 2 inches (5 cm) over the short sides. Grease the paper with vegetable oil or melted butter and lightly dust with flour.
2. For the filling, combine the unsweetened condensed milk, 1 cup of sugar, 3 egg yolks, and diced butter in a saucepan and heat over medium heat. Cook, stirring constantly, until thickened, about 10 minutes. Remove from heat, stir in 1 teaspoon of vanilla extract, the coconut, and the pecans. Set aside and let cool completely, stirring occasionally.
3. Meanwhile, whisk together the flour, baking soda, and salt in a medium bowl. Combine the cocoa and chocolate in another bowl. Add the hot coffee to the chocolate mixture, stirring until smooth; add the buttermilk and the remaining 2 teaspoons of vanilla extract.
4. In a large bowl, beat the softened butter with the remaining 1 1/4 cups sugar with a mixer on high speed until fluffy, about 4 minutes.
5. Reduce mixer speed to low; add 3 whole eggs, one at a time, mixing until fully incorporated after each addition. Add the flour mixture in 3 additions, alternating with the chocolate mixture in 2 additions, beginning and ending with the flour. Knead until the dough is smooth; stir with a rubber spatula if necessary.
6. Spread the batter evenly on the prepared baking sheet. Bake until the cake springs back when lightly pressed, about 16 minutes. Cool slightly on the baking sheet.
7. Run a knife along the edge of the sponge and slide it, along with the parchment paper, onto a work surface. Spread the coconut filling evenly over the sponge.
8. Roll up the short side, peeling off the parchment paper to form a tight roll; transfer to a serving platter. Cool completely and dust with powdered sugar or cocoa powder.