2 egg yolks
3 tbsp. lemon juice
1/2 cup (1 stick) firm butter
1 tbsp. minced onion
1 tsp. tarragon leaves
2 tbsp. white wine

In small pan, stir yolks and lemon briskly with wooden spoon. Stir in one half of the butter and all of the onion and tarragon over low heat until melted. Add the rest of the butter. Stir briskly until butter is melted. Be sure butter melts SLOWLY.

Variation: For Hollandaise Sauce, omit the onion, tarragon, and white wine.