Toward the end of recipe development for my homemade Biscoff, I had amassed a veritable mountain of almost-but-not-quite-there-yet cookies. One batch wasn't cinnamon-y enough, another had a bit too much clove—each one super tasty in its own right, but just shy of copycat perfection. I gave away a ton of cookies, to be sure, but eventually I started grinding my misfit Biscoff and playing with the crumbs. And I wound up developing several crumb-centric recipes, including my summer obsession: homemade Biscoff ice cream.
It's a great way to use up the scraps left over from rolling and cutting these rectangular biscuits. You can also make speculoos (the name for the general category of spiced cookies of which Biscoff is the best-known brand) for the express purpose of ice-cream-ification, if you're hardcore about homemade, but don't worry—store-bought Biscoff work just as well.
Start by crushing up the cookies; you can use a food processor if you like, but it's easy enough with a rolling pin and a plastic bag. Just put some weight into it!
Next, combine Toasted Sugar, egg yolks, and salt, plus a pinch of baking soda, in a three-quart stainless steel saucier. (The baking soda bumps up the alkalinity of the ice cream base, giving it a bit more depth of flavor—something like the savory boost that lye or baking soda can give to homemade pretzels.) From there, whisk in the cookie crumbs, along with some milk and cream.
Start by cooking over medium-low heat to slowly warm the eggs, then increase to medium, and cook until steaming-hot. While it's cooking, you'll want to stir and scrape constantly with a heat-resistant spatula to promote even cooking around the sides of the pan. (And no, I'm not keen on sous vide for this application; stovetop cooking allows for moisture to escape through evaporation, while switching to a plastic bag will produce an icier ice cream.)
Once the ice cream base is steaming-hot, pour through a stainless steel sieve to get rid of any undissolved cookie pieces and knots of chalazae (those firm white bits in an egg). Press gently on the sieve with the spatula to release the flavorful dairy that's been absorbed by the crumbs, but don't smash or press so hard that the pulpy crumbs can pass through. After that, I stir in a small shot of bourbon or rye to boost the overall toastiness of the ice cream, but that's totally optional.
From there, I like to chill my ice cream base in a water bath before refrigeration, though that's mostly my restaurant background talking—refrigerating hot liquids will warm up the fridge, which constitutes a health code violation. With the relatively small volume of ice cream base involved here, it's not a big deal for a home cook to pop it straight into the fridge, so don't feel obligated if you don't have time for the water bath. As long as the base is cooled down to around 39°F (4°C) before churning, it'll do fine.
As former Serious Eats ice cream whisperer Max Falkowitz has explained here, ice cream bases don't need to be chilled overnight. There are some marginal gains to be had, particularly with large batches, but none that are make-or-break when you're just spinning up a quart of ice cream at home.
What will make a difference is your freezer's temperature setting. If it's above 0°F (-18°C), your ice cream canister won't be as cold as it should be, which can result in poor volume and a gooey consistency. But with a properly frozen canister and a well-chilled base, this ice cream will lighten significantly as it churns.
Once it's nice and thick, generally after about 30 minutes, transfer the ice cream to a well-chilled quart container. An empty yogurt tub is great, but if you make ice cream often, it can be nice to have a dedicated container. I have a few, like the one pictured below, from Tovolo.
Before putting on the lid, I like to press a sheet of plastic wrap directly against the surface of the ice cream to keep it from absorbing odors in the freezer. If you plan to eat the ice cream straight away, it's not a necessary step, but it's nice for helping it last over the longer term.
Not that anyone is gonna let this ice cream sit around. It tastes like Europe's favorite biscuit* in frozen form, with notes of caramel, cinnamon, and toasted flour frozen into something creamy, rich, and silky-smooth.
Technically, Biscoff are Europe's favorite biscuit with coffee, so perhaps you should serve your ice cream as an affogato (with a shot of espresso poured on top).
This ice cream is phenomenal scooped up between two Biscoff cookies (homemade or otherwise) for a fancy-pants ice cream sandwich, and even better over a warm bowl of rhubarb crisp (it's the second picture in this series). But to be honest, I mostly eat it straight from the tub when no one's looking. As do other folks in the Serious Eats test kitchen, as I noticed my stash mysteriously dwindled while I was gone.