1. In a saucepan, simmer milk until first bubbles form. Remove pot from heat. In a separate bowl, whisk egg, egg yolk, sweetener and starch.
2. Mash bananas with a fork or use a food processor.
3. Whisking constantly, slowly whisk in the hot milk.
4. Pour the mixture back into the pot and add mashed bananas. Return pot to medium-low heat and gently cook until mixture is thick.
5. Strain through a fine-mesh sieve into a bowl.
6. Mix in the Strawberry powder. Cool to room temperature.
7. Whip the cream.
8. Mix into the cooled milk and banana mixture.
9. Process in the ice-cream machine. If you don't have one, freeze it flat in a large zip-top bag. Then break into chunks to fit inside your food processor. Pulse until smooth and freeze again.