Yield: Icing for 1 (9-inch) cake
1 cup whole milk, divided
2 tablespoons cornstarch
2 egg yolks
6 tablespoons granulated sugar
2 tablespoons unsalted butter
1 teaspoon vanilla extract
1 1/2 cups heavy cream
1/2 to 1 teaspoon rum extract
1 or 2 drops red or pink food coloring (optional)
1. Pour a scant 1/4 cup milk into a medium heatproof bowl. Add cornstarch; stir until it dissolves. Add whole egg and yolks. Whisk well to combine, then set aside.
2. Combine the remaining generous 3/4 cup milk and sugar in a saucepan; bring to a simmer, stirring frequently. While whisking the egg mixture, pour in the hot milk in a slow stream. When all of the milk has been added, pass the mixture through a fine strainer into the saucepan.
3. Cook over medium heat, whisking continuously (see tip), until the mixture comes to a boil and thickens. This will take only a few minutes.
4. Remove from the heat and immediately whisk in butter and vanilla until the custard is smooth.
5. Scrape the hot custard into a nonreactive bowl. Place plastic wrap directly against the surface of the custard; refrigerate until cold.
6. When you are ready to ice the cake, use a stand mixer with the whisk attachment on medium speed to whip the cream just to stiff peaks. Be careful not to overwhip.
7. Transfer the cold custard to a mixing bowl; stir in rum extract to taste. With a rubber spatula, stir in the optional food coloring and a few dollops of whipped cream to loosen the custard. Scrape the remaining whipped cream onto the custard and fold the two together until no visible streaks remain.
Per serving (based on 8): 265 calories; 22g fat; 13g saturated fat; 150mg cholesterol; 3g protein; 14g carbohydrate; 11g sugar; no fiber; 40mg sodium; 75mg calcium.
Tip: To prevent scorching, whisk the custard back and forth rather than in a circular motion.