Slow Cooker Coq Au Vin

4 slices bacon, cut into 1-in pieces
6 bone-in, skinless chicken thighs
8 oz. cremini mushrooms, halved
2 C. frozen white pearl onions, thawed
3 celery stalks, cut into 1-in pieces
2 carrots, cut into 1-in pieces
3 garlic cloves, minced
3/4 C. dry red wine (or sub additional broth)
2 T. tomato paste
1/2 C. low-sodium chicken broth
4 t. arrowroot 
2 sprigs thyme
1 bay leaf
1/4 t. salt
1/8 t. freshly ground black pepper

Lightly oil a 6-qt slow cooker

Cook the bacon in a large nonstick skillet over medium heat until crisp, 6-7 minutes.  Drain on a plate lined with a paper towel.

Pour off all but 1 T. bacon fat from the skillet and return it to the stove over medium-high heat.  Add the chicken, in two batches if necessary, and cook until browned, turning once, about 4 minutes per side.  Transfer to a plate.

Return the skillet to the heat, add the mushrooms, and cook until lightly browned, 3-4 minutes.  Transfer the mushrooms to the slow cooker.

Return the skillet to medium-high heat.  Add the onions, celery, carrots, and garlic and cook, stirring occasionally, until just starting to soften, about 3 minutes.  Transfer the vegetables to the slow cooker and return the skillet to the heat.  Pour in the wine, bring to a boil, and cook for 1 minute.  Remove from the heat and whisk in the tomato paste, broth and arrowroot; pour into the slow cooker and add the thyme sprigs and bay leaf.  Place the chicken thighs on top of the vegetables and top with the reserved bacon.  Cover and cook on low for 7-8 hours, until the chicken and vegetables are tender.  Remove the sprigs and bay lead and season with salt and pepper just before serving.