In a medium saucepan over medium heat, combine 1 cup of whole milk, sugar, and 1 cup of heavy cream. Stir gently until steaming, about 5 minutes. Remove from heat and add mint leaves. Let steep for 1-2 hours.

Mix the egg yolks in a separate bowl. Gently reheat the mint-infused mixture and slowly drizzle over egg yolks, whisking constantly. Return to saucepan and cook over low heat, stirring until thickened—about 5-7 minutes.

Strain the mixture through a fine sieve into a clean bowl, removing mint leaves. Stir in remaining heavy cream and a pinch of salt. Cover and refrigerate for at least 4 hours, or overnight.

In a blender, puree 2 cups of ripe watermelon, 2 tablespoons of sugar, and 1 tablespoon of lemon juice until smooth. Pour into a shallow dish and freeze for 3-4 hours.

Every 30 minutes, scrape the frozen mixture with a fork to create fluffy flakes. Repeat until fully frozen and slushy.

Once the ice cream base is chilled, churn in an ice cream maker until smooth and creamy. Serve layers of mint ice cream with scoops of watermelon granita in chilled glass dishes.

Garnish with fresh mint leaves before serving.