Order a concrete at a custard stand in St. Louis and you will get something that behaves less like a scoop of ice cream and more like a very cold, very rich pudding that has been frozen on purpose. It is dense enough that the straw in your shake stands straight up. It is smooth in a way that makes ice cream feel almost airy by comparison. Ted Drewes on Chippewa has been selling it since the 1930s, and the city has built a small religion around it — but the technique behind it is not complicated, and it does not require a commercial machine the size of a chest freezer.

If you have ever wondered why frozen custard from a Midwest stand tastes different from the best ice cream you can buy at the grocery store, the answer is mostly eggs, mostly fat, and mostly the fact that it never gets much air whipped into it. Here is what is actually going on, and how to get close to it in a home kitchen.

What Makes Frozen Custard Different From Ice Cream

Legally, in the United States, frozen custard has to contain at least 10 percent milkfat and at least 1.4 percent egg yolk solids. Ice cream has no egg yolk requirement at all. That single difference does a lot of work.

Egg yolks bring lecithin, an emulsifier that helps fat and water stay friendly with each other. The result is a base that freezes into smaller ice crystals, which your tongue reads as silk rather than as tiny shards of ice. Yolks also add a faint custardy richness — not eggy if you handle them gently, but rounder and heavier than a plain cream base.

Then there is the churning. Commercial ice cream is deliberately whipped with air, often 50 percent of the volume or more, because air is cheap and volume sells. Traditional frozen custard is churned slowly and served almost immediately, so it holds very little air. A quart of it feels like it weighs twice what a quart of ice cream does. That low overrun is why a St. Louis concrete is so thick that a teenager has to work to turn it over.

Texture, in plain terms

• Ice cream: lighter, airier, firmer in the pint, slower to melt into a puddle.
• Frozen custard: heavier, creamier, softer at serving temperature, melts quickly and pleasingly.
• Gelato: lower fat, denser than ice cream, usually no eggs. Close cousins, different goals.

The Case for Making It at Home

You will not match a stand that churns and serves within minutes. You can get closer than you would expect, and you gain control over flavor. A home batch made with good cream and real vanilla beats most supermarket cartons, and it costs a fraction of what you would pay per scoop at a shop.

The trade-off is planning. The base needs to chill thoroughly — overnight is best — and the finished custard is at its peak within an hour or two of churning. Freeze it solid and it will still taste good, but you will need to let it soften for ten to fifteen minutes before scooping.

A Reliable Home Base Recipe

This makes about a quart. Use a digital thermometer; guessing the temperature is the most common way to end up with scrambled custard.

You will need: 2 cups heavy cream, 1 cup whole milk, 5 large egg yolks, 2/3 cup sugar, 1/4 teaspoon fine salt, 1 tablespoon vanilla extract (or a split vanilla bean steeped in the dairy), and an ice cream machine with a freezer bowl or a compressor.

1. Whisk the yolks, sugar and salt in a heatproof bowl until pale and slightly thickened. Set aside.
2. Warm the cream and milk in a saucepan over medium-low heat until it steams and small bubbles ring the edge. Do not let it boil.
3. Slowly ladle about a cup of the hot dairy into the yolk mixture, whisking constantly. This tempers the eggs so they do not curdle.
4. Pour the warmed yolk mixture back into the saucepan. Cook over low heat, stirring with a spatula and scraping the bottom, until the custard reaches 170°F to 175°F and coats the spatula. This takes five to eight minutes. If you see any lumps, pull it off the heat immediately and strain.
5. Strain the base into a clean bowl. Stir in the vanilla. If you used a bean, fish it out first and scrape the seeds back in.
6. Cool to room temperature, then cover with plastic pressed directly onto the surface and refrigerate at least six hours, ideally overnight.
7. Churn according to your machine's instructions. It will look like soft-serve when it is done — that is correct. Transfer to a cold container and freeze for 30 to 60 minutes to firm up.

Where home cooks go wrong

Undercooking the base is the quiet killer. A custard pulled off the heat at 160°F will taste thin and a little raw. Overcooking past 180°F gives you sweet scrambled eggs. Stay in the window. And resist the urge to churn a warm base; a base that is not fully cold churns into something grainy no matter how good your machine is.

Flavor Tweaks Worth Trying

St. Louis stands are famous for vanilla, chocolate and a rotating list of specials, and the base above is a willing canvas. Steep two split vanilla beans in the dairy for thirty minutes off the heat for a deeper, more floral result than extract gives. For chocolate, whisk 1/3 cup cocoa powder and an extra 2 tablespoons sugar into the yolks before tempering, and add 3 ounces of chopped dark chocolate to the warm strained base so it melts in. For coffee, steep 1/4 cup coarsely crushed beans in the hot dairy, then strain.

Add anything with texture — cookie pieces, nuts, fruit — during the last minute of churning, not the first. Early additions get pulverized and turn the whole batch gray.

Serving It the Way It Is Meant to Be Served

Cold hides sweetness and flavor, so let a home batch sit on the counter for five to ten minutes before serving. Scoop it into a chilled bowl or a heavy glass. A concrete is simply custard with mix-ins folded in hard enough that it holds its shape when the cup is turned upside down — a fun standard to chase, and easier to hit if you fold the add-ins in by hand after churning rather than relying on the machine.

If you are making shakes, use less milk than feels right. The point of a frozen custard shake is that it drinks like a melted milkshake that somehow stayed cold. Start with a splash, blend, and add more only if the blender stalls.

A Few Practical Notes Before You Start

Eggs are the backbone here, so use fresh ones and keep the base refrigerated until the moment it goes into the machine. If you are cooking for anyone pregnant, elderly or immunocompromised, note that the custard base is cooked to 170°F or higher, which is above the temperature generally recommended for egg safety, but check with a healthcare provider if you have any doubt about your own situation.

Make the base the night before you plan to serve. Freeze your storage container while the machine runs. And keep expectations calibrated: this will be very good, and it will not be Ted Drewes. That is fine. It is close enough that you will want to make a second batch before the first one is gone.

Photo: Terje Sollie / Pexels