In a 4-Cup Prep Bowl, whisk eggs until foamy. Add mix and water; whisk until well combined.
Microwave, uncovered, on high for 2 min, until thickened, whisking halfway through and at the end. If the curd has not thickened after 2 min, cook for additional 30 sec intervals, whisking after each, until desired thickness is achieved.
Whisk in butter, if desired.
Cover; refrigerate for at least 1 hour, or until cooled.
Per serving (1 tbsp): Calories 35, Fat 0.5 g (Saturated 0.2 g, Trans 0 g), Cholesterol 25 mg, Sodium 10 mg, Carbohydrate 7 g (Fiber 0 g, Sugars 6 g), Protein 1 g.
Make Lemon Tarts! Fill prebaked, cooled tart shells with cooled prepared curd. There is enough filling to fill 12 tart shells or 24 mini tart shells.