While bacon is frying whisk together the butter, cornstarch, thyme, salt, and pepper.
Whisk in wine and garlic. Stir in bay leaf. Set aside.
Layer in a large Crock-Pot: potatoes, shallots, celery, carrots, chicken, bacon, mushrooms, and top with parsley. Do not stir.
Pour wine seasoning mixture over chicken and vegetables.
Cook on low for 4 to 6 hours.
When the chicken is cooked, remove about a cup of wine and whisk 1 to 3 tablespoons of crème fraîche into the wine. Pour it back into the Crock-Pot and stir.