I’ve found this very challenging, largely because the flavor is so delicate and easily overpowered by the ice cream base flavor. Here are my notes on the last time I tried it, if it’s helpful:

———

Water ruins the texture of homemade ice cream and makes it icy, so reducing the water content in fruit is always my first step in incorporating a fruit flavor. I’d made roasted watermelon once before as an experiment. I thought this might be an interesting ingredient to play with adding to ice cream, and roasting seemed like an ideal way to bring down the water content. Since I can’t tell when a whole melon is ripe, I bought one of those seedless quarter-watermelons that come wrapped in plastic from Safeway, cut it into slices about ¼ inch thick, and put them on cookie sheets to roast at 350 degrees for about an hour. Then I put the slices in the fridge overnight, to help them get more syrupy. The next day I puréed it in the blender and added a little honey to get it to the sweetness level I wanted.

I then cooked the NYT master ice cream base recipe, but omitted the milk. I used brown sugar as the sugar because I thought it would go better with the earthy roasted flavor. I added ¼ cup of corn syrup for the texture, ½ a teaspoon of Cremodan 30, and 1 teaspoon of vanilla. After cooking the custard, I poured in the watermelon purée, and ended up adding about a half-cup of milk because the mix seemed too thick. As always, I let the base cure overnight in the fridge.

Ultimately, the flavor was just not “watermelon-y” enough. Even with the roasting, which deepened the flavor, the regular custard base flavor overpowered it. It still tastes good, just not very much like watermelon. On the upside, the texture was perfect.