Magnolia Bakery's Orange Vanilla Cupcakes

Cupcake Ingredients
1 ½ cups self-rising flour
1 ¼ cups all-purpose flour
1 cup (2 sticks) unsalted butter, softened
2 cups sugar
1 tablespoon freshly grated orange zest
4 large eggs, at room temperature
1 cup orange juice (use a variety without pulp)
1 teaspoon vanilla extract
Frosting Ingredients
3 tablespoons all-purpose flour
1 cup whole milk
1 cup (2 sticks) unsalted butter, softened
1 cup sugar
1 teaspoon vanilla extract
Unsweetened shredded coconut, for garnish (optional)

Instructions
To make the cupcakes:
1. Preheat the oven to 350. Line two 12-cup muffin tins with cupcake papers.
2. In a small bowl, combine the flours. Set aside.
3. In a large bowl, on the medium speed of an electric mixer, cream the butter until smooth. Add the sugar and zest gradually and beat until fluffy, about three minutes. Add the eggs, one at a time, beating well after each addition.
4. Add the dry ingredients in three parts, alternating with the orange juice and vanilla. With each addition, beat until the ingredients are incorporated but do not over beat. Using a rubber spatula, scrape down the batter in the bowl to make sure the ingredients are well blended.
5. Carefully spoon the batter into the cupcake liners, filling them about three-quarters full. Bake for 20 to 25 minutes, or until a cake tester inserted into the center of the cupcake comes out clean. Cool the cupcakes in the tins for 15 minutes. Remove from the tins and cool completely on a wire rack before icing.

To make the frosting:
1. In a medium-size saucepan, whisk the flour into the milk until smooth. Place over medium heat and cook, stirring constantly, until the mixture becomes very thick and begins to bubble, 8 to 10 minutes. Cover with waxed paper placed directly on the surface and cool to room temperature, about 30 minutes.
2. In a large bowl, on the medium-high speed of an electric mixer, beat the butter for three minutes, until smooth and creamy. Gradually add the sugar, beating continuously, and mix until fluffy, for three minutes. Add the vanilla and beat well.
3. Add the cooled milk mixture and beat for five minutes, until very smooth and noticeably whiter in color. Add a few drops of red food coloring to give a pink tint to the frosting, if desired. Cover and refrigerate for 15 minutes (no less and no longer—set a timer!). Use immediately to frost the cupcakes. If you like, garnish with the coconut (or do some with coconut and some without).