Step 1

Place butterfly pea flowers in a jar and pour in vodka. Cover the jar and shake gently. Let the mixture infuse for at least 15 minutes (or up to an hour for the best color). Strain through a fine-mesh sieve; discard the flowers and reserve the vodka. (You'll have more blue vodka than you need for these cocktails; refrigerate any extra for up to 1 week.)

Step 2

To sugar the rims (if desired): Place sanding sugar in a small shallow dish. Place honey in a second small shallow dish. Dip the rims of each of 2 wineglasses into the honey and then into the sugar.

Step 3

Combine 3 ounces of the infused vodka, crème de menthe (or mint syrup), ice cream and ice in a blender; blend on high until smooth. Divide between the prepared glasses (or 2 wineglasses) and serve.