Preheat oven to 350°F (180°C).
Within the bowl of a stand mixer fitted with the paddle attachment, beat butter and sugar at medium pace till fluffy, 3 to 4 minutes, stopping to scrape sides of bowl. Add eggs, one by one, beating properly after every addition. Beat in vanilla.
In a medium bowl, whisk collectively flour, baking powder, and salt. In a small bowl, whisk collectively yogurt and milk till mixed. With mixer on low pace, add flour combination to butter combination in three additions alternately with yogurt combination, starting and ending with flour combination, beating simply till mixed after every addition.
In one other medium bowl, whisk collectively melted chocolate and espresso powder till espresso absolutely dissolves. Stir in half of batter.
Spray a 6-cup charlotte cake pan with baking spray with flour. Spoon plain and chocolate batters in an alternating sample into ready pan. Firmly faucet pan on a kitchen towel-lined counter to settle batter. Utilizing a picket choose or skewer, swirl batters collectively.
Bake till a picket choose inserted in heart comes out clear, 25 to half-hour. Let cool in pan for 10 minutes. Invert cake onto a wire rack, and let cool utterly.
Simply earlier than serving, unfold Whipped Mascarpone onto cooled cake, and sift cocoa on prime. Refrigerate in an hermetic container for as much as 3 days.
