Place 3 chopped rhubarb stalks into a milk pitcher and add 20 bar spoons of granulated sugar
Cook for 10 minutes while stirring
Pour into a blender and blend
Pour 9 bar spoons of the resulting rhubarb puree, 0.35 oz of lime juice and 0.5 oz of sugar syrup into a mixing glass
Add 1 vanilla pod
Fill the glass with ice cubes and stir
Strain into a chilled cocktail glass
Top up with champagne and stir gently
Garnish with a half of a stalk of rhubarb