Ingredients:
Prepare crepes or bring to room temperature if refrigerated. Melt butter in a Dutch oven; add onion and cook over medium heat, stirring occasionally, until limp and pale gold, about 30 minutes.
Meanwhile, remove stems from spinach, wash thoroughly, drain briefly, and tear into bite-sized pieces. Add spinach to onions, cover, and cook until limp, about 2-3 minutes. Stir in cream, salt, and lemon juice. Over high heat, cook, stirring, until most of the liquid is evaporated. Divide filling and cheese equally between crepes, spooning it down center of each; roll to enclose. If made ahead, you can freeze crepes by placing them seam-side down without touching on greased baking sheets. Freeze uncovered, then package air-tight. For best flavor, use within 2-3 weeks.
To serve, arrange desired number of fresh or frozen crepes in a shallow casserole or individual ramekins. Cover with foil and bake in a 375 oven for about 20 minutes (or 35-40 minutes if frozen). Remove cover and bake 5 minutes longer or until ends of crepes are crisp. Before serving spoon sauteed mushrooms over crepes; accompany with sour cream. Full recipe makes 6-8 servings.