Add the cauliflower to a saucepan and pour over enough boiling water to come up halfway over the florets. Cover with a lid and cook on a medium heat for 5 minutes. The cauliflower should be just soft. Drain well and leave to cool.
Add the cauliflower to a food processor along with the cream alternative. Blitz until smooth.
Pour the cauliflower mixture into a bowl and add the milk, sugar, sweetener and vanilla and whisk with a balloon whisk until the sugar and sweetener have dissolved. Add the cocoa powder and whisk again until creamy and combined.
Pour into your Ninja Creami tub. Pop the lid on and freeze for 24 hours.
Remove the tub from the freezer and use the light ice cream function on your Ninja Creami machine. If your ice cream looks chalky or not a nice creamy consistency, use the re-spin function. We used the light ice cream function once and re-spin once. Serve.