In a medium saucepan, heat cream, milk, and lavender flowers until mixture comes to a simmer. Remove from the heat and cover. Allow to steep for 20 minutes.
In a medium heat-proof bowl, whisk together sugar, egg yolks, and flour. Mixture will be very thick. Add 4 to 5 tablespoons of milk mixture to thin yolk mixture out. Whisk until yolks turn pale yellow, about 1 minute.
Slowly whisk the hot milk mixture into the yolks to temper them. Pour the custard back into the same saucepan.
Whisk constantly over medium heat until custard thickens slightly – about 2-4 minutes.
Remove from heat and strain into a bowl set over an ice water bath.
Add food coloring if desired and whisk well.
Allow mixture to cool completely. Remove from ice water bath and cover with plastic wrap.
Chill in the refrigerator several hours or overnight, until mixture is very cold. Process custard in ice cream machine according to manufacturer’s directions.
Pack ice cream in an air-tight container and store in the freezer.