For the cake: Place an oven rack in the center of the oven. Preheat the oven to 325 degrees F. Spray an 11- by 8-inch rimmed baking sheet with cooking spray. Lay a piece of parchment paper over the baking sheet allowing the excess to fall over the sides. Spray the parchment paper with the cooking spray. Set aside.
In a medium bowl, whisk together the flour, cocoa powder, baking powder and salt. Set aside.
In a stand mixer fitted with a paddle attachment, beat the butter and granulated sugar on high speed until light and fluffy, about 1 minute. Beat in the eggs, one at a time until smooth. Add the mascarpone cheese, orange juice and zest. Mix until well combined. Gradually add the flour mixture until combined.
Scrape the batter into the prepared baking sheet, spreading the batter to the edges. Bake until a cake tester comes out clean, 12 to 15 minutes. Cool in the pan for 30 minutes. Using the excess parchment to lift, carefully remove the cake from the baking sheet and cool completely on a wire rack for about 30 minutes.
For the frosting: While the cake is cooling, combine the confectioners' sugar, milk, vanilla extract and butter in a medium bowl. Using an electric hand mixer, combine the ingredients until smooth, adding more milk if needed (the frosting should be stiff). Gradually add the orange food coloring until desired color.
Cut the cooled cake in half. Using a serrated knife, trim the top layer of cake halves to make a flat surface. Spread the frosting over one half of the cake. Top with the other cake half. Refrigerate for 45 minutes to 1 hour until the frosting has set.
For the chocolate: Combine the chocolate and safflower oil in a small bowl and place over a saucepan of barely simmering water. Stir occasionally until the chocolate has melted and the mixture is smooth.
Line a baking sheet with waxed paper. Cut the cake into 1 1/4-inch squares. Insert a popsicle stick into the end of each cake square. Dip the cake squares into the melted chocolate, shaking off any excess chocolate. Decorate with sprinkles and place on the prepared baking sheet. Repeat with the rest of the cake squares. Refrigerate the pops until the chocolate has set, 1 to 2 hours.