In a small saucepan, combine 2 cups half-and-half and basil. Bring just to a boil over medium-high heat; remove from heat, and let stand for 30 minutes. Strain mixture through a fine-mesh sieve into a container, discarding solids. Cover and refrigerate half and-half until very cold, about 2 hours.
In a large bowl, beat cream with a mixer at medium-high speed until stiff peaks form. Add sweetened condensed milk, and beat until stiff peaks form again. Gradually pour in basil-infused half-and-half and remaining 2 cups half-in-half, stirring until combined.
Pour mixture into the container of an electric ice cream maker. Stir in crushed blueberries. Freeze mixture according to manufacturer’s instructions. Spoon mixture into freezer-safe containers, and freeze for up to 1 month.
Spoon desired amount of ice cream into glasses. Fill with chilled ginger ale. Garnish with blueberries and basil, if desired, and serve immediately.
Recipe by Victoria at https://victoriamag.com/blueberry-basil-ice-cream-floats-recipe/