Spray a mini muffin pan with nonstick spray and set it aside. Prepare the chocolate chunk cookie batter with the vegetable oil, water, and egg according to the package directions. Cover the batter and chill in the refrigerator for at least one hour.
Preheat oven to 350 degrees F. Scoop one tablespoon of chilled dough and roll it into a ball. Place the ball in one of the cups of the prepared mini muffin pan. Spray the back of a teaspoon with cooking spray and press the teaspoon onto the ball of dough to create a divot. Use your fingers to further form a cup so the dough forms around the sides and up to the top of the muffin cup. Repeat to fill the rest of the cups.
Bake the cookie cups for 12 to 16 minutes or until the cups are set and the edges begin to pull away from the sides. If the dough puffs up, tap the top of the cookies so that it sinks back into the cups. Let the cookies cool completely in the muffin pan. Use a sharp knife to loosen the cups from the edges of the pan and remove the cookie cups.
To make pots of gold, spoon a dollop of the prepared pudding in the cookie cup, top generously with gold sugar sprinkles and place two or three Lucky Charms marshmallow bits on the sprinkles.