- Pour gelatin in a small container and add water; set aside.
- Puree raspberries in a blender. Strain to remove seeds and measure 1 cup. Use any remaining amount to flavor sparkling water, etc.
- Pour raspberry puree in a saucepan large enough to hold all ingredients. Add egg whites and sugar.
- Whisk raspberry mixture for 1 minute. Place over heat and whisk vigorously to 180°F or until mixture develops bubbles on side of pan.
- Remove from heat and add gelatin mixture. Whisk to combine.
- Allow to cool to 120°F (warm shower water). Add butter and stir using a spatula.
- Pour in a dish and place in the refrigerator. After 4 hours or overnight stir the mixture vigorously until it becomes smooth and creamy.