Remove Krusteaz Professional Ready to Bake Chocolate Cake & Muffin batter #732-0610 and Ready to Bake Sweet Cream Vanilla Cake & Muffin Batter #732-0625 from refrigerator. No slacking required.
Prepare two 16x12x1-inch half-sheet pans by lightly greasing, lining with parchment paper and then lightly greasing the parchment paper. If using a pan extender (recommended), lightly grease the sides of the pan extender.
Cut open one end of the chocolate pouch and squeeze half of the batter into each prepared pan.
Cut open one end of the sweet cream vanilla pouch and squeeze half of the batter length-wise in a long striping motion so you can see some of the chocolate batter underneath.
Use a knife and without touching the bottom of the pan, move the knife across the batter back and forth and from side to side the length of the pan. Then use the same motion going the other way down the pan. You'll see a swirl as the batters begin to show a marbling pattern.
Repeat in the second pan.
For convection oven, bake at 300°F at low fan speed for 25-30 minutes, turning pan halfway through bake time.
Allow cake to cool completely before cutting or removing from pan.