Start by making the beetroot juice. After thoroughly cleaning the beets, ideally, peel them with the peeler, cut them into small pieces and put them in the juicer.
Meanwhile, in a bowl mix the beetroot juice, cream, zest, and lemon juice.
In a small bowl add the cornstarch together with 2 tbsp. milk, stir until dissolved.
In a saucepan add the milk, sugar and basil leaves. Do not chop the leaves as we want to remove them later. Simmer on medium heat until sugar melts.
Remove the basil and then add to the mixture to the cornstarch and stir vigorously until the mixture begins to thicken.
Remove from heat and add to the mixture the beet juice. Leave aside and let it cool completely. Ideally, let it cool in the fridge for one night.
Add the mixture in the ice cream machine and follow the instructions of the ice cream machine. If you do not have an ice cream machine you can see the notes above on what to do.
Usually, ice cream needs around 20-30 minutes to the ice cream machine maker. Shortly before completing the process, add the walnuts.
Transfer to a container suitable for freezing and place in the freezer for about 2-4 hours, or until it freezes completely.