Step 1: Prepare the Watermelon Granita - Chop watermelon chunks and blend with sugar and lemon juice until smooth. Pour into a shallow dish and freeze for about 3-4 hours, scraping every 30 minutes.

Step 2: Infuse the Cream for Ice Cream - Combine whole milk, sugar, and 1 cup of heavy cream in a saucepan. Heat until bubbles form, then add mint leaves and steep for 1-2 hours.

Step 3: Temper the Egg Yolks - Whisk egg yolks until smooth. Reheat the mint mixture and slowly add to the yolks while whisking, then combine back into the saucepan.

Step 4: Thicken the Ice Cream Base - Cook mixture over medium heat, stirring, until it thickens, about 5-7 minutes. Strain through a sieve to discard mint leaves.

Step 5: Finish the Ice Cream Base - Add remaining heavy cream and salt to the strained mixture. Cool to room temperature, then refrigerate overnight.

Step 6: Churn the Ice Cream - Pour into an ice cream maker and churn until soft-serve consistency, about 20-30 minutes. Freeze for at least 4 hours.

Step 7: Assemble the Float - Scoop watermelon granita into glasses, add mint ice cream, and drizzle with sparkling rosé.