First make the rhubarb puree by taking the rhubarb, water and Grenadine and place in a microwave proof bowl, covered. Cook this in a microwave on high for 3 1/2 minutes. When cooked, blend until smooth.
Now bring the cream to a simmer, add the puree and bring back up to the boil.
Beat the egg yolks and sugar together.
Soak the gelatine in very cold water.
Gradually pour the rhubarb and cream infusion in with the egg yolks mixing all the time, remove the gelatine from the water, ring out well and add to the mix.
Place the ice cream mix back onto a stove and mix constantly but do not boil and only cook the mix until it coats the back of a spoon.
Pour into the ice cube tray and freeze until solid.
Serve with Tristan's Easy Custard Ice Cream.