In the same skillet, cook shallots for a few minutes until they brown a bit.
Pour them into your slow cooker.
Add broth, 1/2 cup of your sherry (reserve 1/4 cup for later), mushrooms and leeks.
Cook on low for 8 hours.
Then add half and half, remaining sherry, butter, sugar and salt and pepper to taste.
Stir well and serve.
If you do not want to use the shallots and leeks, you can substitute one medium onion chopped and use it during the shallot step (and as a replacement for the leeks as well.If you do not want to use sherry, replace with beef broth.If you do not want to use crimini (baby bella mushrooms) you can use white button mushrooms instead.Note: Nutritional information including calorie count varies based on exact ingredients you choose to use.