Wash the mushrooms well. (baby bellas tend to be a lot dirtier than button mushrooms) Take a wet paper and gently wipe any remaining dirt away.
Place mushrooms in a slow cooker.
Melt the 2 sticks of butter on the stove or in a microwave and melt. Add the 2 packets of seasoning to the melted butter and mix well with a fork or whisk and mix well.
Pour mixture over mushrooms in slow cooker. Cook on low for 3 hours. **note if serving in a different bowl, pour mushrooms and sauce into the bowl. Even though the butter sauce looks oily, it holds the flavors so do not dump out. Use a slotted spoon to retrieve the mushrooms.
Very important to serve hot. I would suggest to serve in your slow cooker or in a chafing dish.