Dice the 2 onions into bite-sized pieces, chop the 3 celery stalks into ½-inch pieces, and cut the 1.1 lb carrots into 1-inch chunks. Measure out the flour, thyme, garlic powder, salt, and pepper into a small bowl. Cook the 7 oz bacon in a skillet over medium-high heat until crispy, about 8-10 minutes, then transfer to a paper towel and crumble once cooled. This prep work ensures everything is ready to layer into the slow cooker efficiently.

Pat the 2.2 lb chicken thighs dry with paper towels—this helps the flour adhere better and promotes browning. Season the chicken pieces generously with salt and pepper, then dredge them in the flour mixture from Step 1, shaking off any excess. Layer the diced onions, chopped celery, carrots, and crumbled bacon from Step 1 into the bottom of your slow cooker to create a flavorful bed for the chicken.

Arrange the floured chicken pieces on top of the vegetable and bacon layer in the slow cooker. In a small bowl, whisk together the 1.5 cups chicken stock, 2 tbsp mustard, thyme, garlic powder, salt, and pepper until smooth. Pour this liquid around (not directly over) the chicken to gently distribute the flavors throughout the casserole. I prefer pouring around the sides rather than over the top so the chicken stays moist and doesn't get waterlogged.

Cover the slow cooker and cook on HIGH for 4 hours or on LOW for 6 hours, depending on your time availability. The chicken should be very tender and easily pull apart with a fork when done. I like to use the LOW setting when possible because it keeps the chicken even more tender and allows the flavors to develop more gradually.

Once the cooking time is complete, stir the 4 tbsp creme fraiche into the hot casserole—the residual heat will incorporate it smoothly without curdling. Gently fold in the 3 tbsp fresh parsley, then taste and adjust seasoning with additional salt and pepper as needed. The creme fraiche adds richness and a subtle tang that balances the mustard and herbs beautifully.