Crabby Pot Pie

2 T. plus ½ c. butter, divided3 c. chopped leeks1 c. chopped celery1 c. chopped carrots¼ c. flour2 c. peeled, diced russet potatoes2 (8-oz.) bottles clam juice1 T. lemon zest2 t. Old Bay Seafood SeasoningSalt, red pepper to taste1 c.…