1preheat the oven to 325°. Butter and flour a 9 inch square baking pan.
2To make the brownies, mix the flour, cocoa, baking powder, and salt in the top of a double boiler over boiling water. Do not allow the bottom of the pan to touch the water. Add the chocolate chips and cook, stirring until the chocolate melts and the mixture is smooth. Remove and let cool for 10 minutes.
In a large bowl, mix the eggs, butter, and 1/2 cup water. Add the powdered sugar, buttermilk, food coloring, vinegar, baking soda, and vanilla. Beat the mixture with electric mixer until smooth. Stir in the chocolate mixture. Pour the mixture into the prepared pan.
3Bake for 40 minutes or until the top is set and a knife inserted in the center comes out clean. Remove from the oven and set the pan on a rack to cool.
4Meanwhile, to make the frosting, heat the condensed milk, butter, and chocolate chips in a pan over medium heat. Cook, stirring constantly, until the chocolate chips melts. Remove from the heat and let cool. In a mixing bowl, beat together the egg yolks and powdered sugar with electric mixer until fluffy. Add the chocolate mixture and beat until thick. When the brownies are cool, spread the frosting over top, makes 12 brownies.