Preheat the oven to 350ºF (170ºC). Spray a 9" springform pan2 with non-stick spray. Set aside.
In a large bowl, whisk together the flour, cornstarch, baking soda, and salt. Set aside.
2 and ¼ cup (270g) all-purpose flour, 2 teaspoons (5g) cornstarch, 1 teaspoon baking soda, ¾ teaspoon salt
In a medium size bowl, whisk together the butter, brown sugar, and granulated sugar until smooth. Whisk in the egg, egg yolk, and vanilla extract until completely combined.
¾ cup (171g) unsalted butter, 1 cup (200g) firmly packed brown sugar, ¼ cup (50g) granulated sugar, 1 large egg + 1 large egg yolk, 2 teaspoons vanilla extract
Pour the wet ingredients into the dry ingredients and stir until no flour lumps remain. Fold in the chocolate chips and sprinkles. Press the cookie dough evenly into the prepared pan. Bake for 23-25 minutes until edges begin to brown. You may cover the cake with foil to prevent browning, if preferred. Remove from oven and allow to cool on a wire rack completely before decorating with frosting.
1 cup (170g) chocolate chips1, ⅓ cup (33g) orange sprinkles
VANILLA BUTTERCREAM GHOSTS
In a large bowl with a handheld mixer or a stand mixer fitted with the paddle attachment, beat the the butter on medium-high until smooth, about 2 minutes.
½ cup (113g) unsalted butter
Reduce the mixer to low, then slowly add the powdered sugar and mix until everything is combined. Add the vanilla extract and mix again.
2 cups (240g) powdered sugar, ½ teaspoon vanilla extract
Slowly add the milk or cream, watching for and stopping at desired consistency. Add the salt, then increase the mixer speed to medium and beat until completely smooth.
2 to 3 Tablespoons (30-45mL) milk or cream, ⅛ teaspoon salt
If after beating, the frosting is too stiff, add more cream. If it is too thin, add more powdered sugar, about 2 Tablespoons at a time.
Turn off the mixer and use a spatula to stir the buttercream by hand to remove air bubbles and make it smooth and creamy. This usually takes about 3-5 minutes, but can take longer, especially if your mixer is very strong.
Remove cooled cookie cake from springform pan and place on serving platter. Fill a piping bag with the frosting and pipe ghosts onto cookie cake. Add two candy eyeballs per ghost. You can also decorate this Halloween cookie cake however you desire! If using, add sprinkles before frosting sets. Store leftovers covered tightly at room temperature for up to 5 days. Undecorated cookie cake may be frozen, up to 2 months. Thaw in refrigerator overnight and allow to come to room temperature before decorating.
candy eyes, Halloween sprinkles
Notes
Chocolate chips:I prefer ½ milk and ½ semi-sweet chips, but realistically, you can put any kind of chips you like in this cookie cake.
Springform pan: alternatively, you may use a 9" pie plate or a 8" or 9" round or square baking pan.
All nutritional values are approximate and provided to the reader as a courtesy. Changing ingredients and/or quantities will alter the estimated nutritional calculations.