To make the syrup, in a blender, combine the rhubarb and sugar. Pour in the boiling water, cover the blender, and blend until completely puréed. Strain through a fine mesh sieve and store the syrup in an airtight jar for up to a couple weeks in the refrigerator. Reserve the pulp for another use, like spreading on buttered toast or scones or stirring into some sautéed garlic and ginger to make a topping for pork tenderloin.
To make the cocktail, put 3/4 ounce of the chilled syrup in a cocktail coupe or Champagne flute, then top with the Prosecco. Adjust the amount of rhubarb syrup to taste.
I like to say I'm a lazy iron chef (I just cook with what I have around), renegade nutritionist, food policy wonk, and inveterate butter and cream enthusiast! My husband and I own a craft distillery in Northern Minnesota called Vikre Distillery (www.vikredistillery.com), where I claimed the title, "arbiter of taste." I also have a doctorate in food policy, for which I studied the changes in diet and health of new immigrants after they come to the United States. I myself am a Norwegian-American dual citizen. So I have a lot of Scandinavian pride, which especially shines through in my cooking on special holidays. Beyond loving all facets of food, I'm a Renaissance woman (translation: bad at focusing), dabbling in a variety of artistic and scientific endeavors.