Mix, shake, strain in coupe.
Rhubarb syrup: 4 stalks, peel rhubarb, chop, heat with 7 oz water, let boil, and rhubarb get to the point of purée. Strain, then strain again with coffee flter. Add same volume sugar. Bottle. Fridge.
Rhubarb tartness is going to vanish slowly after a week. Maybe some malic or citric acid could remedy to the problem.