Preheat oven to 350F.
In the bowl of a stand mixer, fitted with the paddle attachment cream together butter and sugar. Scrape the sides and bottom of the bowl and add eggs and vanilla. Beat to combine.
Add flour, cornstarch and salt. Beat until incorporated, for 3-4 minutes. Shape into a ball.
Roll out the dough between 2 pieces of parchment or wax paper, it needs to be around 1/4 -inch thick.
Cut out 3 different sizes of stars.
Place on baking sheets and bake for 12-15 minutes (depending on the size, keep an eye on the cookies).
Let the cookies cool.
Melt chocolate with vegetable oil.
Stack together cookies with melted chocolate, place the biggest size on the bottom, and smaller ones on top. Drizzle with chocolate. Top with sprinkles.