Sift first 4 ingredients; set aside.
Cream butter and sugar with electric mixer fitted with paddle attachment on medium speed until light and fluffy. Add eggs, 1 at a time, beating well after each. Add water; mix until combined.
Add dry ingredients all at once. Mix on low speed until combined. Scrape side of bowl; mix 20 seconds more.
Portion 8 oz. batter into each of 14 (6-inch) cast iron skillets. Sprinkle each with 2/3 oz. OREO Pieces and 1 Tbsp. chocolate chunks.
Bake in 350°F standard oven 20 min. or until wooden pick inserted in centers comes out clean. Serve warm, topping each skillet with 3 #30 scoops of Cookies and Cream ice cream. This is a dessert for 2 to share.