Boston Cream Doughnut Holes

INGREDIENTS:

For the doughnut holes:
1 cup all-purpose flour
1/4 cup granulated sugar
1 teaspoon baking powder
1/2 teaspoon salt
1/2 cup milk
1 egg, lightly beaten
2 tablespoons unsalted butter, melted
Oil, for frying
For the custard filling:
1/2 cup milk
2 tablespoons granulated sugar
1 egg yolk
1 tablespoon cornstarch
1 teaspoon vanilla extract
For the chocolate glaze:
1/2 cup semisweet chocolate chips
2 tablespoons heavy cream
1 tablespoon corn syrup
1/2 teaspoon vanilla extract

DIRECTIONS:

In a large bowl, whisk together flour, sugar, baking powder, and salt. In another bowl, mix milk, egg, and melted butter. Combine the wet and dry ingredients until just mixed.
Heat oil in a deep fryer or large pot to 350°F (175°C). Carefully drop teaspoon-sized balls of dough into the hot oil. Fry until golden brown, about 2 minutes per side. Remove with a slotted spoon and drain on paper towels.
For the custard, heat milk and sugar in a small saucepan over medium heat until hot but not boiling. In a bowl, whisk together egg yolk and cornstarch. Gradually whisk in hot milk. Return mixture to the saucepan and cook over medium heat, whisking constantly, until thickened. Remove from heat, stir in vanilla extract, and let cool.
For the chocolate glaze, combine chocolate chips, heavy cream, corn syrup, and vanilla extract in a microwave-safe bowl. Microwave in 30-second intervals, stirring in between, until smooth.
Once the doughnut holes and custard have cooled, use a piping bag with a small nozzle to inject custard into each doughnut hole. Dip the top of each filled doughnut hole into the chocolate glaze.
Let the glaze set before serving.