1 stick (4 oz.) unsalted butter
1 cup diced onion
2 cups diced celery
1½ Tbs. kosher salt
1 Tbs. pepper
1 qt. chicken stock
3 heaping Tbs. roughly chopped fresh sage leaves
3/4 cup heavy cream
2 stale baguettes, (1.25 lbs.), cut into large dice
Melt the butter in a medium saucepan over low heat. Add the onion, celery, salt, and pepper and cook, covered, for 20 to 25 minutes or until soft. Keep the lid on to avoid browning and stir often. Remove from heat and let cool.
In a large bowl, combine the onion and celery mixture with the remaining ingredients and toss well. Place into a 9x13-inch casserole dish, cover with plastic wrap, and refrigerate overnight.
Bake uncovered at 350°F for one hour and 30 minutes.
Pro Tip: The uncooked dressing can be prepared, placed in an aluminum pan, covered, and frozen up to two months in advance. Simply defrost and bake as directed. Serve hot or warm.