In a bowl mix together flour, 1 cup brown sugar, 3 T cocoa, baking powder and salt.
In a different bowl combine milk, butter and vanilla.
Combine the two bowls of wet and dry ingredients until they are just combined and then spread in the crock.
Sprinkle peanut butter chips evenly over the top of the batter.
Combine remaining ingredients with the boiling water and stir until dissolved.
Pour over the top of the batter and do not stir.
Place paper towels over the top of the crock and place lid on top.
Cook on high for 1 to 4 hours until cake is set and sauce on the edges is bubbly.
Spoon out into bowls and serve with ice cream.
Like I said before, Mikey made this in the casserole crock with success, but then we made it again in a 6 qt Ninja Slow Cooker and we loved how it crocked up even thicker and more evenly than the casserole crock.
"Baking" times varied GREATLY depending on the slow cooker we used. The casserole crock took about 3.5 hours while our 6 qt only took 90 minutes! So, like we always say make sure to try this for the first time when you have time to watch it and adjust your time.
This cake turns out to be a lot like a lava cake that you spoon out, not a traditional cake that you cut slices off to serve.