- Turn the slow cooker on high and place butter in the bottom. While it’s melting, make garlic easy to separate and peel by placing the heads on a cutting board and banging their tops with a meat mallet or heavy pan. Separate the cloves and whack them again. Peel off the skins and give another whack to slightly smash them.
- Add the Dijon and cornstarch to the soft butter in cooker and mash together. Pour in the wine. Whisk until fairly smooth. Add the smashed garlic cloves and chicken. Sprinkle with tarragon and salt. Turn chicken pieces to coat with tarragon.
- Slice onion in half and place cut-side down on a cutting board. Thinly slice and scatter over chicken, separating as you add. Cover and cook on high for 4 hours or medium for 6 hours. If you are able, stir chicken half way through the cooking–but this is not essential.
- Arrange cooked chicken on mashed potatoes or rice. Mash the garlic into the sauce and spoon onions and sauce over all.
Remember this recipe when you spy those big plastic bags of peeled garlic that pop up in the produce section of supermarkets. They’re inexpensive and any not used right away can be frozen.