Add 150 g granulated sugar, ¼ teaspoon xanthan gum, and ¼ teaspoon fine sea salt to a medium saucepan and whisk until completely combined.
Take 2 tablespoons of the 360 g whole milk and whisk it together with 15 g corn starch. Add it to the saucepan along with the remaining milk and 240 g light corn syrup and whisk to combine.
Cook over medium heat while whisking until the mixture comes to a gentle simmer and thickens slightly, 3-4 minutes. Take off the heat, whisk in 720 g heavy cream and chill until completely cool.
Divide roughly equally into 3 separate bowls. To the first bowl, add 2-3 drops of blue gel food colouring and ⅛ teaspoon LorAnn bubblegum flavour oil, and mix to combine.
To the second bowl, add 2-3 drops of purple gel food colouring and ⅛ teaspoon LorAnn grape flavour oil, and mix to combine.
To the third bowl, add 2-3 drops of yellow gel food colouring and ⅛ teaspoon LorAnn banana cream flavour oil, and mix to combine.
Churn each flavour separately, according to the instructions for your ice cream maker. Keep the other flavour bases in the fridge until they're ready to churn. After each flavour is churned, put it in the freezer for at least 8 hours to firm up.
After all three flavours have been churned and frozen, alternate scooping the three flavours into a container. Gently swirl them together to just slightly combine them.
Enjoy! This ice cream should keep well in your freezer for at least 1-2 weeks.
