Start by preheating your oven and greasing the mini muffin pan well. In a mixing bowl, combine the yellow cake mix, softened butter, and eggs. Mix until a thick, smooth dough forms; it will be slightly sticky, which is normal.
Scoop the dough into the muffin pan, filling each cavity evenly. Lightly press the dough down so it spreads slightly. Bake until the tops are just set and lightly golden. While warm, gently loosen the edges and let them cool completely in the pan.
In a clean bowl, combine the pudding mix, heavy cream, and milk. Whip until the mixture becomes thick and holds stiff peaks. This step is key for a creamy but stable filling.
Once the cookie cups are fully cooled, pipe the vanilla cream into the center of each one. Fill generously so the cream slightly rises above the edges.
Heat the chocolate chips and cream together until melted. Stir until smooth and shiny. Spoon a small amount of ganache over each filled cookie bite and allow it to set.