Whisk water and egg together in a microwave safe bowl. Add the lemon filling mix and whisk until smooth. Microwave for 1 minute. Remove from microwave and whisk. Return to microwave for an additional 30 seconds. Remove and whisk again. Repeat for additional 30
seconds at a time, whisking after each time until filling is smooth and the consistency
of pudding. If filling gets too thick you can whisk in water, a tablespoon at a time,
until desired consistency, Whisk in 2 tablespoons butter until melted. Carefully spoon filling into small parfait glasses or shot glasses. Chill and top with whipped cream.