Spray crock pot with cooking spray
Combine flour, sugar, 4 T cocoa, baking powder and salt
Add milk, oil and vanilla and stir
Gently stir in one bag of peanut butter chips
Place in your crock pot and spread evenly
Combine brown sugar and 8 T cocoa in separate bowl
Stir in hot water
Pour mixture evenly over batter (do NOT stir)
Pour your second bag of peanut butter chips evenly across the top
Cover and cook on high for 1½ - 2 hours, until cake passes toothpick test
Turn off crock pot and remove lid
Let cake stand for 30-40 minutes
Serve cake and spoon chocolate lava from bottom of crock pot over cake