In a medium saucepan, combine whole milk, sugar, and heavy cream over medium heat. Stir gently and watch for bubbles forming around the edges—about 5 minutes. Remove from heat.

Add fresh mint leaves to the warm milk mixture, cover, and let steep for 1 to 2 hours.

Whisk egg yolks in a separate bowl until smooth. Reheat the mint-infused milk mixture over low heat.

Gradually ladle warm milk mixture into the yolks, stirring constantly to prevent scrambling. Pour back into saucepan and stir until thickened (5-7 minutes).

Strain the mixture through a fine mesh sieve into a bowl, stir in remaining heavy cream, cover, and refrigerate until completely chilled (ideally overnight).

Pour chilled mixture into ice cream maker and churn for 20-25 minutes until soft-serve consistency. Transfer to airtight container and freeze for 2-3 hours.

In a food processor, puree watermelon, sugar, and lemon juice until smooth.

Pour the watermelon mixture into a shallow freezer-proof dish and freeze for about 30 minutes.

Use a fork to scrape the partially frozen granita every 30 minutes for about 3-4 hours until fully frozen and fluffy.

Serve the mint ice cream in bowls and top with the granita. Sprinkle with flaked sea salt before serving.