Can I use chicken breasts instead of thighs?
Yes. Breasts are leaner, so they can dry out if you push the time too long. Cook on LOW for 3 to 4 hours, but start checking early (around 2 1/2 to 3 hours), depending on thickness and your slow cooker model. You want 165°F in the thickest part.
Will the lemon turn the chicken tough?
Usually not in this setup. The lemon juice is diluted in a saucy cooking liquid, and the slow cooker stays moist. That said, if you are sensitive to sharp acidity or you just want to play it extra safe, use the zest at the start and stir in half the lemon juice at the end for maximum brightness.
How do I make it less tangy for kids?
Use 1 tablespoon Dijon instead of 2, and bump the honey to 2 tablespoons. You still get flavor, just softer around the edges.
Can I add vegetables to the slow cooker?
Definitely. Add sliced onions with the chicken. For sturdier veggies like carrots, add them at the start. For quick-cooking veggies like green beans, stir them in during the last 30 to 45 minutes on HIGH so they do not get sad.
What if my sauce is thin?
Two fixes: (1) Use the cornstarch slurry as written. (2) After thickening, leave the lid off on HIGH for 10 to 15 minutes to reduce a little more.
Any tips to keep the sauce from getting greasy?
If your thighs have a lot of visible fat, you can trim a bit before cooking. After cooking, you can also skim excess fat from the surface of the sauce with a spoon before thickening.