Melt the butter and sauté the garlic in it for three minutes. Blend in the flour.
Drain the clams, reserving them. Pour the juice from the clams into a measuring cup. Measure out twocups, adding as much additional bottled clam juice as necessary. Slowly add to the butter and flour mixture, stirring.
Add the parsley, salt and pepper to taste and the thyme. Bring the mixture to a boil and simmer for ten minutes. Add the reserved clams and reheat. Serve over the linguine. Top with grated cheese if desired.