Combine the milk with 2 cups Fruity Pebbles™, stir to combine, and steep for 13 – 15 minutes. Don’t steep any longer than that. Strain the milk through a fine mesh sieve into a large liquid measuring cup. Don’t press the Pebbles™ really; just leave them there for a bit to drain as much as possible. You should end up with 2 cups of fruity, infused milk—if not, add a little more to make up the difference.
Add the heavy cream and infused milk to a large heavy bottom pot and put over medium-low heat to bring to a scald.
Meanwhile, whisk the egg yolks, sugar, and salt together in a bowl until you have a, thick, pale, and slightly voluminous base—about 2 – 3 minutes. When the whisk is lifted out of the bowl, the yolks should fall off the whisk in an even, continuous ribbon.
Now that the cream is scalding, temper the eggs by whisking a ladles-worth of hot cream into the them. Do this a few times before pouring the rest of the cream into the yolks. Wipe the pan out, and pour the custard mix back into it through a fine-mesh sieve, to catch any coagulated bits of egg.
Cook the custard over medium-low heat, stirring and scraping down the sides with a rubber spatula all the while, until it’s thick enough to coat the back of a wooden spoon, and when you run your finger across the spoon it stays divided—about 12 – 15 minutes.
Pour it immediately through a fine mesh sieve set over a heatproof bowl to ensure that the final product comes out perfectly smooth.
Cover the custard with plastic wrap directly on the surface and let it cool to room temperature before moving to the fridge for at least 6 hours—it has to cool completely before you can even consider churning.
While you wait on the custard base to cool, melt the 2 cups mini marshmallows, and 1 tablespoon butter in a medium saucepan over low heat, stirring constantly. Scrape down the sides and bottom with a rubber spatula so nothing sticks and, once everything is completely melted and smooth, fold in the remaining 2 cups of Fruity Pebbles™. Toss to combine before turning out onto a parchment-lined baking sheet. Spread it out into an even layer, cool to room temperature, and then refrigerate until it’s fairly solid. Break it up into bite-sized bits.
Once the custard is chilled, churn in your ice cream maker per its instructions. Remove the churning paddle, fold in the Pebbles™ clusters, and transfer to a storage container and freeze a few hours, at least, before serving.
I don’t throw the Fruity Pebbles™ clusters into the ice cream machine while churning to let the paddle fold them in—I don’t want them to break up too much. Just use a rubber spatula to fold them in before transferring to a freezer-bound storage container.
If you've never made a custard before here is my little spiel on exactly how to do so:
First, grab a wooden spoon, rubber spatula, whisk and heatproof glass bowl. These are your new appendages. Where you go, they go… but you’re not going anywhere once that burner is back on under the custard. Don’t even try it. You might think you have enough time to answer the doorbell, let the dog out or make a cup of coffee while you cook the custard but its already one step ahead of you. It knows what you’re going to try and the second you step away from it – BOOM – sweet, creamy, scrambled eggs.I also advise you to follow Nigella Lawson’s instructions of filling your sink with cold water and ice so that, should the custard start to curdle as you cook it, you can plunge the pot into the sink and whisk ferociously until the custard smoothens back out.
Turn the burner back onto medium-low and stir frequently and vigilantly, switching between the wooden spoon and rubber spatula to help scrape the sides and bottom of the pan and prevent any sticking.
Once it’s thickened and cooked, immediately pour out through a fine mesh sieve and into a heatproof glass bowl.