Sprinkle gelatin over lemon rind and lemon juice in a small saucepan; let stand 1 minute. Cook over low heat, stirring until gelatin dissolves (about 2 minutes). Add cream and next 3 ingredients. Cook, stirring constantly, over low heat until smooth. Remove from heat; stir in sour cream and lemon rind. Cool completely; chill thoroughly.
Spoon mousse mixture in center of crêpes. Fold crêpes in half, then in half again to form a triangular shape. Place 2 filled crêpes on each of 4 individual serving plates. Spoon warm Lemon Sauce over crêpes, and garnish, if desired.
*For testing purposes only, we used Melissa's crêpes.
Tip: Be sure to grate the rind from the lemons first before squeezing the juice. Grate rind and squeeze juice for the mouse and Lemon Sauce all at once to save time.