Beat milk, eggs, sugar, cocoa, vanilla and salt in a medium bowl.
Grease a 1-quart casserole. Cut the croissants into 1-inch pieces and layer half in the casserole along with the chocolate chips, and half the egg mixture. (I use the crock pot insert.) Repeat layers with remaining croissants and egg mixture.
Add a rack to a 5-quart crock pot. Pour in 1 cup water. Place casserole on rack. Cover and cook on LOW 3 to 4 hours. Remove casserole from crock pot. Top each serving with 2 tablespoons whipped cream, if desired.
Note: I did make this in my 3-1/2 quart crock pot with no problems.