Melt
the butter over medium heat in a large, heavy pot. Add the flour; stir constantly for 5 minutes until a golden
roux is formed. Add the onion and
continue to cook until onion becomes golden, 5 to 7 more minutes. Add the celery, red pepper, scallions,
and garlic, and cook until all are softened, about 5 more minutes. Add approximately 1 C. water and season
with Tabasco®, salt and pepper.
Stir in the langostinos and parsley, reduce the heat to low, and simmer
for 10 minutes. Serve at once over rice.