In a separate, large bowl, stir together your oil, vanilla, egg whites and eggs until well blended
Gently pour your flour mixture into your egg mixture and stir until completely combined
Stir in your melted chocolate
Spray your 3-4 quart crock pot (I used Corky, my Hamilton Beach Multi-Quart Slow Cooker on the 4-quart setting) with cooking spray and pour in your batter
Place 3-4 paper towels under the lid to catch any moisture from dripping on the cake
Cover and cook on low for 2 hours (the sides should be set, but the middle should be soft)
Leave the lid on your crock pot, but turn it off and let the cake stand for about 30 minutes