In another large bowl, whisk together yogurt, the 1 1/4 cups granulated sugar, the oil, egg product, buttermilk, and vanilla. Add yogurt mixture to flour mixture; beat with a wire whisk just until combined. In a medium bowl, combine cocoa powder and the 2 tablespoons espresso powder. Add half of the yogurt mixture (about 2 cups) to the cocoa mixture, stirring until smooth; set aside. Add the reserved 1/2 cup flour to the remaining yogurt mixture, whisking just until combined.