Fisherman's Stew with tomatoes, root vegetables and baby potatoes

Olive Oil
2 Tbsp. Butter
1# firm white fish (Cod, Haddock, etc.)
1# mixed seafood (Trader Joe's seafood medley / calamari, shrimp, scallops)
2 med. Onions, thinly sliced
1 med. bulb Fennel, thinly sliced
2 ribs Celery, thinly sliced
3 Carrots, peeled cut into 1" pieces
1 Parsnip, peeled cut into 1' pieces
2 cloves Garlic, peeled and minced
1 cn. diced Tomatoes
1# baby potatoes (red bliss/fingerlings, etc.), cut into similar sized pieces
1/3 c. half & half (optional)
1 btl. Clam Juice
1/2 c. fish stock ( can sub. chicken stock)
bay leaf
fresh thyme, fine chopped, to taste
Old Bay seasoning, to taste
salt and pepper, to taste
Corn Starch (for thickening)
Crusty bread (french baguette)

Put large pot over medium high heat.  Add oil, heat until shimmering.  Add onions, fennel, and butter.  Cook for 5-6 minutes making sure to stir often, they should be cooked until translucent; add garlic cook 2 minutes.  Add potatoes, carrots and parsnips, cook 2 minutes.  Add clam juice, stock, half & half, and tomatoes (with juice).  Add Bay leaf, thyme, and Old Bay; cook for 10 minutes.  Add all seafood and cook until fish is just done 8-10 minutes.  Adjust seasoning with salt and pepper.
While the fish is cooking, as an optional step if you like the stew to be a little thicker, make a slurry.  This is done by placing a couple of tablespoons of corn starch in a small bowl and while stirring, add just enough water to it that the consistency resembles heavy cream.   Increase heat under the stew until mixture is bubbling and while stirring add small amounts of slurry to stew.  Do this in stages as not to over thicken.  Once  stew is thick enough lower heat, cook 2 more minutes and then serve with crusty bread.