Step 1In a large saute pan, melt the butter and saute the leeks over low heat until tender, about 5 minutes.
Step 2Add the wine, cream, salt and pepper and simmer gently until reduced by two-thirds. Add the scallops and shrimp and stir until the shrimp is pink and the seafood cooked, about 5 minutes. Stir in the tarragon, lemon juice and creme fraiche.
Step 3Spoon about one-half cup of the mixture onto a buckwheat crepe, fold in half and serve immediately.