For the streusel topping:
- 1 18- or 19-ounce package Mexican chocolate, roughly chopped
- 1 large egg yolk
- 3 1/2 ounces (7 tablespoons) butter, at room temperature
- 1 cup (4 1/2 ounces) all-purpose flour
For the cake:
- 1 3/4 cups (8 ounces) all-purpose flour
- 1 1/4 teaspoons baking powder
- 8 ounces cream cheese, at room temperature
- 8 ounces (16 tablespoons) unsalted butter, at room temperature
- 2/3 cup granulated sugar
- 4 large eggs, at room temperature
- Powdered sugar, for dusting the finished cake
The streusel topping. In a food processor, pulse half of the Mexican chocolate until it is the consistency of coarse crumbs. Remove and set aside for the batter. To the processor, add the second half of the chocolate and process it to the consistency of coarse crumbs. Mix the egg yolk and 1/2 teaspoon salt (if using salted butter, omit the salt) in a small bowl to dissolve the salt. Add to the processor along with the 3 1/2 ounces butter, and the 1cup flour. Pulse the machine just until everything is thoroughly combined — it should look crumbly, not having been processed to a paste.
The cake. Heat the oven to 350 degrees. Butter and flour a 13 x 9-inch baking pan. Sift together the 1 3/4 cups flour and baking powder. In the bowl of an electric mixer on medium speed, combine the cream cheese, the 8 ounces butter and the sugar. Beat until light and fluffy, 2 to 3 minutes. One at a time, add the eggs, beating until one is thoroughly incorporated before adding the next. Add the sifted flour mixture, scrape down the sides of the bowl and beat for 1 minute, just until the flour is incorporated. Lastly, use a large spoon to stir the reserved chopped chocolate into the batter.
Scrape the batter into the prepared pan and smooth. Crumble the streusel topping evenly over the batter, making sure there are no large lumps — lumps may sink during baking.
Bake in the center of the oven until springy (the edges will have just begun to pull away from the sides of the pan) and a toothpick inserted at the center comes out clean, 35 to 40 minutes.
Cool on a wire rack (in my opinion, this cake tastes best when still slightly warm), cut into squares and serve dusted with powdered sugar. Vanilla, caramel or cinnamon-scented ice cream sure goes well with a bite of this pastel.