Creating Boston Cream Pie Cookie Dessert can be fun and straightforward if you follow these steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Prepare a baking sheet by lining it with parchment paper.
2. Make the Cookie Dough: In a bowl, whisk together the flour, baking powder, and salt. In another bowl, cream the softened butter and sugar until light and fluffy. Add the egg and vanilla extract, mixing well.
3. Combine Mixtures: Gradually add the dry ingredients to the wet ingredients, stirring until just combined.
4. Scoop the Dough: Use a cookie scoop to drop rounded tablespoons of dough onto the prepared baking sheet, leaving space between each cookie.
5. Bake: Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden. Remove from the oven and let cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.
6. Prepare the Vanilla Custard: In a saucepan over medium heat, whisk together the milk, cornstarch, sugar, vanilla extract, and egg yolks. Cook until the mixture thickens, stirring constantly. Remove from heat and stir in the butter until melted. Allow the custard to cool.
7. Assemble the Cookies: Once the cookies are completely cool, use a piping bag or spoon to fill each cookie with the cooled vanilla custard.
8. Make the Chocolate Glaze: In a microwave-safe bowl, combine the chocolate chips and vegetable oil. Microwave in 30-second intervals, stirring until smooth.
9. Glaze the Cookies: Drizzle or dip the filled cookies in the chocolate glaze, allowing any excess to drip off. Let the glaze set.
10. Serve: Once the glaze has hardened, the cookies are ready to be enjoyed!