Roasted Koji Ice Cream Recipe

Koji, which is the mold grown on barley or rice to produce miso, adds sweetness, umami, and floral flavors to many dishes. But when koji is roasted, it reveals its hidden desire to taste a bit like chocolate.

For a couple pop-ups in San Francisco, I served a roasted koji ice cream that juxtaposed koji’s dessert-like flavor profile with the acidity of raspberry and depth of thyme. In this post, I’ll provide the recipe for both making the roasted koji ice cream itself and for prepping the dessert in its final form: a sundae served with freeze-dried raspberries, brown butter koji caramel, thyme, and cornflower.

If you’ve read about my recipe development process, you’ll know that I test everything regularly and often. But this recipe for roasted koji ice cream was perfect on the first try. It makes no sense — people absolutely love it, so I am too afraid to change it.

Using oven-roasted barley koji, freeze-dried raspberries, brown butter koji caramel, thyme, and cornflower, the recipe is at once sweet, acidic, savory, and floral. Even if you don’t make the whole dessert, the brown butter koji caramel is ridiculous!

Roasted Koji Ice cream

The first step is to make the roasted koji ice cream. I grow my own barley koji for this recipe. If you’d like to learn more about growing koji, see here. Otherwise, here is some rice koji (which will have a fairly similar taste) on Amazon.

We’re going to roast the koji before infusing a vanilla ice cream base with it. This gives the koji a chocolatey smell that subtly transforms the taste of the vanilla ice cream into a new taste altogether.

To roast the koji, simply put at least 200g of it in the oven at 250ºf until it is very fragrant and lightly browned throughout — just like you would do when roasting almonds. Like almonds, if you go too far with it, it’ll be bitter like bad coffee. So be careful. It should take about hour, but I’m hesitant to give an exact time because the water content of your koji will make a big difference on the cooking time.

Once you’ve roasted the koji (which you can do a couple days in advance), it’s time to create an ice cream base and infuse it with the roasted koji.

I make my ice cream base sous vide to ensure that the infusion is consistent and the base does not curdle. To do so, I use my Breville Joule.

The ice cream base recipe is as follows:

1. Preheat water bath to 185ºf.

2. Blend together 250g whole milk, 90g of sugar, 5 egg yolks and seeds from one vanilla pod with a stick-blender.

3. Stir in 250g of whipping cream, being careful not to whip it.

4. Transfer the mixture to a freezer ziploc bag alongside 100g of the roasted koji.

5. Cook the mixture for 60 minutes, occasionally agitating the bag to ensure that the koji is mixed in.

6. Transfer the mixture to an ice bath to rapidly chill it, then strain it and put it in the fridge.

7. The next day, make ice cream from the mixture using your ice cream machine’s directions. Store in freezer until its time to eat.

Koji brown Butter Caramel

This will be less viscous than a traditional caramel. It lasts a couple weeks in the fridge.

1. In a medium sized saucepan, add 3/4 cup of butter.

2. Put the pan on medium heat. Once the butter begins to bubble, add a handful of dehydrated koji (not roasted yet — they will look like cocoa pebbles in a few minutes regardless!).

3. Continue stirring the butter/koji mix until the butter browns.

4. As soon as the butter browns, add 1/2 cup of cold buttermilk to the saucepan. Immediately add 3/4 cup of sugar and continue mixing until the sugar dissolves.

5. Once the mixture begins to boil, add a teaspoon of vanilla extract and 1 teaspoon of baking soda. The whole mixture will foam like crazy! This is why we chose the medium saucepan instead of the small :)

6. Once the foaming subsides, strain and store in a glass container that you can put in hot water to reheat before serving the ice cream.

Roasted Koji Ice Cream Dessert

Putting it all together! There are a few more ingredients you’ll need:

1. Thyme. I prefer fresh micro-thyme that you can use stems and all.

2. Cornflower. I grow my own cornflower but I’m sure many places sell it near you. The cornflower is just for the aesthetic.

3. Maldon salt

4. Butter cookie crumble: For my popups, I just bought Dansk butter cookies and crumbled them up!

5. Freeze-dried raspberry powder: Here’s what I buy.

Cornflower and thyme ready to be placed on ice cream.

Here are the instructions:

1. Take the roasted koji out of the freezer 20 minutes before serving.

2. Put roasted koji ice cream in a bowl.

3. Imprint a hole in the center of the ice cream with your spoon, then pour some of the roasted koji caramel into the hole.

4. Dust freeze-dried raspberries over the top. I do so with a little strainer.

5. Add the cookie crumble to a corner of the dish.

6. Garnish with the thyme and cornflower. When serving this in bulk (like my popups), I mix the thyme and cornflower together in advance.

7. Top with a small pinch of maldon salt.