Begin making your Boston Cream Pie Cookies by creaming together the unsalted butter and granulated sugar in a large mixing bowl until light and fluffy, about 3-5 minutes. Add in the eggs, one at a time, along with the vanilla extract, mixing until fully combined. Gradually incorporate the flour, baking powder, baking soda, and salt, blending just until combined. Chill the dough in the refrigerator for 30 minutes.

While the dough chills, prepare the filling by whipping the heavy cream with powdered sugar and vanilla extract until soft peaks form, about 3-4 minutes. Set the pastry cream aside in the fridge to keep it cool while you bake the cookies.

Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper. Scoop the chilled cookie dough into rounded tablespoons and place them on the baking sheets, leaving space for spreading. Bake for 12 minutes or until the edges are lightly golden. Cool on the baking sheets for a few minutes before transferring to a wire rack.

To make the chocolate glaze, combine the chocolate chips and vegetable oil in a microwave-safe bowl. Heat in 30-second intervals, stirring in between, until smooth and melted.

Once cookies are cooled, slice each in half horizontally, fill the bottom half with pastry cream, and dip the filled top into the chocolate glaze. Allow excess glaze to drip off before placing on a wire rack to set.