Step #6 Potatos may be scrubbed & left unpeeled if prefered.
Step #7 Cut carrots into 3-inch lengths & cut the celariac into chunks about the size of golf balls.
Step #8 If using celery scrub, trim, & cut into 4-inch chunks.
Step #9 Drain tomatoes.
Step #10 Reserve juice for another purpose if desired.
Step #11 Heat olive oil In a large-ish, heavy skillet & brown the chicken pieces thoroughly.
Step #12 Drain on paper to absorb excess fat.
Step #13 Place vegetables & garlic clove into a large, tightly-lidded roasting pan.
Step #14 Arrange chicken pieces on top of the vegetables with the herbs on top of the chicken.
Step #15 Pour 1 c chicken stock into the dutch oven.
Step #16 Drizzle 1 tbs sherry evenly over the chicken pieces.
Step #17 Roast covered at 250F for 3-4 hrs or until chicken is cooked through & vegetables are tender.
Step #18 Remove chicken to a warmed serving platter & keep hot.
Step #19 Remove vegetables to a warmed serving bowl, disgarding the thyme, parsely, garlic & celery.
Step #20 Keep hot.
Step #21 Pour out the pan juices into a bowl & skim away any excess fat.
Step #22 Return one c of the defatted pan juices to the dutch oven along with the cream & the other 2 tbs sherry.
Step #23 Add the celery seed, salt, & pepper.
Step #24 Cook on medium-low heat on the stovetop until just simmering.
Step #25 Whisk the cornstarch into the milk then add this mixture to the pan.
Step #26 Stir constantly until the gravy simmers.
Step #27 Continue to simmer 2-3 mins, stirring constantly with the whisk until the gravy thickens.
Step #28 If more gravy is desired there should be plenty of pan juices to make it -- just keep the proportions the same to retain the richness.
Step #29 Serve each person chicken & vegetables then pass the gravy boat.
Step #30 I'd suggest a salad of romaine or butterhead lettuce or buttered green beans as sides & would recommend hearty, crusty bread or rolls to help mop up the gravy.
Step #31 If you have a very large platter it would make a pretty presentation to arrange the chicken in the middle surrounded by vegetables, drizzled with the gravy, & garnished with a bit of fresh parsley.