To get hardened chocolate off of dishes fill the sink with some boiling hot water and then place the dishes with the hardened chocolate in the boiling water.
The boiling water should melt the hardened chocolate so that it comes off more easily.
Then use some white vinegar in the water to get the chocolate out of the dishes.
When the chocolate is hard you need to melt the chocolate to get it off the dishes.
The chocolate should always melt again using the boiling water or putting the bowl or other dish in the microwave to get the hardened chocolate to melt.