Heat the heavy cream and whole milk in a saucepan over medium heat until steaming, not boiling, about 3–5 minutes, until you see small steam bubbles around the edges. Keep the heat steady and watch for the first simmer-like signs.

Whisk the egg yolks and granulated sugar in a bowl until smooth, then slowly whisk the hot cream mixture into the yolks in a thin stream. Continue whisking until the mixture looks glossy and evenly combined.

Return the mixture to the saucepan and cook, stirring constantly, until it reaches 175°F, about 5–8 minutes. The custard should visibly thicken enough to coat the back of a spoon; scrape a line with your finger and it should hold.

Strain the custard through a fine mesh strainer into a clean container, then whisk in the cotton candy flavoring or extract, vanilla extract, and salt. It should taste sweet and smell strongly of cotton candy.

Divide the strained custard into two bowls, one for pink and one for blue, keeping them the same amount for balanced swirls. Add pink and blue food coloring and stir until the colors are vivid and uniform.

Cover both bowls and chill completely in the refrigerator until cold throughout, about 3–4 hours. The custard should be fully chilled with no warmth at the center.

Churn each chilled custard separately in an ice cream maker until soft-serve consistency, following your machine’s timing. The mixture should look thick and aerated when you stop the machine.

For the swirl effect, alternate scooping the two colors into a freezer-safe container while layering them, or layer as you transfer from the churned batches. Aim for ribbon-like streaks so the pink and blue stay distinct.

Freeze until firm, about 2–4 hours, until it holds a scoop cleanly. The texture should be thick and scoopable, not fluffy.

Top with cotton candy right before serving to keep it airy. Add a small tuft centered on top for the carnival look.

If you prefer, churn one base first, then swirl in both colors during the freeze step by layering spoonfuls of pink and blue on top. Keep layering gently so the swirls remain visible rather than fully blending.