Making soft serve is hard. We wanted to make high-end, all-natural, really good tasting soft serve, but there are some real challenges. The main one: You can't put chunks through the machine. So strawberry with chunks of berry? Forget it.
We thought we'd start with the basic: vanilla. The classic soft-serve flavors are chocolate and vanilla, and we thought, if we can't do vanilla and chocolate right, we have no business doing this. We made up a simple mixture similar to an ice cream recipe: a gallon of whole milk and two pints of cream with five vanilla beans steeped in a big pot, about four cups of sugar, and a teaspoon of sea salt. Oh, and two tablespoons of guar gum. It's a stabilizer, a powder made from a bean, you buy it in bulk at health food stores. Two tablespoons is an outrageous amount to use, by the way, but we didn't know that then. We took that mix, we strained it, we drove it out to where we had the machine, we poured it in, we switched the machine on, and we crossed our fingers. And it came out great! Not perfect, there was room for tinkering, but so much better than any other soft serve we'd ever had.
That made us a little cocky. But not for long. When we tried to make the ice cream richer and add more vanilla flavor, bad things started happening. The machine started making weird noises and the ice cream wouldn't come out. Or it would come out and it was grainy and weird. What was going wrong? We put our hands into the ice cream and felt it. It felt gummy and sticky. Maybe the guar gum was the problem? It was! We started decreasing the amount. We felt the grainy lumps too, and figured they were fat globs! So we began decreasing the amount of fat in the recipe.
Fruit flavors are tough! When you can't have chunks of actual fruit in the ice cream, it's hard to get an intense flavor. We ordered these "all natural" fruit extracts, but they didn't smell or taste right. I'm looking at the blueberry one right now; the ingredient list says "water, organic ethyl alcohol, and natural flavors." We ended up doing a thing where we'd juice the fruit, make a syrupy reduction with sugar, then mix that with the milk. We had to mess around with the proportions of everything so it didn't get too icy. We haven't tackled strawberry yet, because of the difficulty in straining out the seeds. Citrus is one of the easiest: it has a nice, powerful flavor and big seeds that are easy to get out. But citrus juice also curdles milk. Turns out that if you refrigerate the citrus syrup and the milk and cream mixture separately before mixing them together, they're more stable and can play with each other.
Coffee was another tough flavor. It's hard to get it so the coffee flavor is strong but not bitter, and the ice cream isn't icy because you put too much water in it with the coffee. We ended up going to Blue Bottle Coffee for advice. They gave us their recipe for New Orleans iced coffee. You coarse grind the beans and cold-soak them overnight in water. And that worked! I don't know why though. I recently tried using this same method with regular hard ice cream, and it came out terrible. We also tried using milk to cold-soak the coffee, and it came out bitter. It tasted just like coffee grounds smell.
At this point, we've got a lot of wonderful flavors. Mojito, butterscotch, mint, honey-blueberry, brown sugar-ginger, lemon thyme and molasses spice. My personal favorite is the nutmeg. It has five nutmeg seeds in each batch. You have to grate the nutmeg by hand, and it takes about an hour. You can't put it in the food processor because you get chunks. I don't think nutmeg really gets you high, but I do like to think about that as I'm grating away.
We've also made some terrible flavors. Pumpkin was nasty. We tried to make a green curry flavor with bananas and apple for fruitiness and Thai green curry paste. It ended up tasting like banana garlic and we threw it away.