Heat the oven to 350°F and keep the eggs close to 70°F because cold eggs can make the oil sit apart from the dry cake mix. For Halloween Cake Mix Cookies, stir the French vanilla cake mix with the eggs, canola oil and vanilla for 60 to 75 seconds. Scrape from the bottom with a flexible rubber spatula. Then fold in the Halloween candy-coated milk chocolate pieces, mini semisweet chocolate chips and orange purple and green jimmies sprinkles with six broad turns. Stop early. Overmixing makes the dough tight and the baked centers less tender. The dough should look thick and slightly glossy, with colorful pieces still visible instead of crushed into the mix. If it runs like batter, the eggs were likely too warm or oversized. Brief mixing limits gluten and keeps the centers tender.

Keep the oven at 350°F while you portion the dough for Halloween Cake Mix Cookies into 18 mounds of about 1 1/2 tablespoons each. Work within 5 minutes so the oil doesn't keep softening the mix. Roll each mound once between your palms, then set nine on each baking tray about 2 inches apart and press two or three extra Halloween candy-coated milk chocolate pieces on top. Don't pack the balls firm. Dense shaping slows the spread and leaves thick cakey centers. The mounds should hold a rough round shape, but small cracks and uneven candy placement are welcome. If they slump before baking, chill the trays at 40°F for 10 minutes. Loose shaping leaves room for the dough to spread.

Bake one tray of Halloween Cake Mix Cookies at a time on the middle rack at 350°F for 9 to 11 minutes, so the edges set without drying the center. At minute 6, rotate the tray from front to back with one smooth turn so the outer cookies don't darken first. Pull the tray when the edges look set but the centers still seem slightly soft. Go past 11 minutes and the bottoms can harden. (I baked my first batch for 13 minutes. They lost the soft middle I wanted.) You should smell warm vanilla and chocolate while the tops turn matte with a few shallow cracks. The centers will still look soft. Pulling them early lets carryover heat finish the centers without drying them.

Within 60 seconds of each tray leaving the 350°F oven, press two small candy eyeballs into every cookie in the Halloween Cake Mix Cookies batch while the tops are still soft. Let the cookies stand on the tray for 5 minutes, then cool them for 10 more minutes at about 70°F before moving them to a serving plate. The centers settle slightly and the edges firm as heat escapes. Wait too long to add the eyes and they won't grip the surface. The finished cookies should have soft centers, lightly crisp rims and uneven patches of orange, purple and green candy. Let them settle. Move them too soon and the warm cookies can split. Cooling sets the crumb so each cookie lifts cleanly.