Initial Preparation: Preheat the oven to 350 degrees Fahrenheit. Generously spray each cup of a mini muffin pan with non-stick cooking spray.
Making the Dough: In a medium-sized bowl, whisk or sift the vanilla cake mix to eliminate lumps. Add vegetable oil and eggs to the cake mix. Combine using a hand mixer until the dough achieves a thick and sticky consistency.
Forming the Cups: Employ a small cookie scoop or measure out approximately 1/2 tablespoon to transfer a portion of cookie dough into each muffin cup. Press down each mound of dough to create a level cookie surface.
Baking: Bake the cookie cups in the preheated oven for 9 to 11 minutes. Avoid overcooking; the cups will firm up as they cool.
Shaping the Cups: After baking, run a knife around the edge of each cookie cup to loosen it (an offset butter knife is recommended). Use a tart shaper or the end of a wooden spoon to press down the center of each cookie cup, creating a well for the filling. Transfer the cups to a cooling rack and let them cool completely. If necessary, repeat the baking process for the remaining dough.