By James P. DeWan

Chicago Tribune

There are a number of ways to produce delicious ice cream at home without the use of special machinery or newfangled contraptions. Before we get to a couple of them, though, let’s talk about what ice cream is, not because you don’t know, but because perhaps you’ve never really thought about why we make it the way we do and what happens when it’s made.

Here’s how ice cream traditionally is made. After combining ingredients, the cold, liquid mixture (called the “base”) is churned in a machine whose parts are icy cold. The “icy cold” part allows the creamy base to freeze from liquid to solid. The churning mixes air into it, increasing the volume, lightening the mouthfeel and softening the finished product, so you don’t end up with an unscoopable — albeit tasty — giant white ice cube.

And here’s a boring bonus fact about that air: The phrase “overrun” refers to the amount of air that’s churned into ice cream. If you start with 1 gallon of base, for example, and you churn into it enough air to end up with 2 gallons of ice cream, that’s called a 100 percent overrun. Trot that one out next time there’s a conversational lull at the cocktail party.

(Check out the recipe below, and you’ll see how we get air into the mixture using whipped cream.)

Now, a couple of methods for homemade ice cream without the machine, both of which are predicated on moving the base across an ice cold surface, thereby freezing it into ice creamy submission.

The enclosure-within-a-larger-enclosure method

The idea is to put the base in a container and seal that container inside another, larger container along with some salted ice (more on salted ice in a minute).

You can use two plastic bags (one that is pint- or quart-sized, the other quart- or gallon-sized). Or you can use two different-sized coffee cans or plastic food storage containers. Anything that can be sealed securely and will give you plenty of room for ice will work.

Regardless of your containers, seal the ice cream base along with any flavoring ingredients in the smaller one, and place it inside the larger. Add enough salted ice to the larger container to fill completely. (You want about 1/2 cup coarse kosher salt or table salt per 4 to 6 cups of ice.) Seal the larger container, then shake them together until the base freezes into ice cream — often in 5 minutes or so. Open the small container, and enjoy the fruits of your labor. (If the ice cream hasn’t set, shake some more. Or put it in the freezer until set.)

The ice-cold-pan method

Place a heavy, shallow pan or bowl or a smooth slab of marble (you have a large, smooth slab of marble lying around, don’t you?) in your freezer for several hours or overnight, enough to be colder than Ayn Rand’s heart. Pour your base and your flavoring ingredients onto the surface, then set it back in the freezer for 15 to 20 minutes, just enough for it to start to freeze on the edges. Take it out, and use a spatula to scrape it over onto itself several times. You can also use a whisk or, if you’re really crazy, an electric hand mixer.

For smaller amounts of base, the surface will be cold enough to continue freezing it while you mix and you can get ice cream in just a few minutes. For larger amounts, you’ll need to mix it a few minutes, then put it back in the freezer for 20 minutes again to continue freezing.

Either way, though, you’ll soon enough have what appears to be — and, more important, tastes exactly like, because that’s what it is — delicious ice cream that you made yourself.

Salted ice

Why do we salt the ice when we make ice cream?

First of all, regular tap water freezes at 32 degrees Fahrenheit. That means ice water, because it’s a mixture of ice and water, is right around 32 degrees Fahrenheit, the temperature at which freezing water turns to ice and, consequently, thawing ice turns back into water.

Salt water, on the other hand, won’t freeze until it reaches a much lower temperature; the more salt, the colder the temperature needed to freeze the water.

Let’s assume you’ve added enough salt to make the water freeze at 20 degrees F — no problem in a home freezer that’s probably about 0 degrees F. Now, if you take that ice out of the freezer, when it gets back to 20 degrees, it’ll melt back into water. Regular ice, on the other hand, won’t turn back into water until it reaches 32 degrees. And that’s why salted ice water (or icy salt water) is always colder than regular water. Dig?

And if you’re making ice cream, that means that the colder the ice water, the faster our base is going to freeze into our yummy, yummy dessert.

Simple ice cream base

Adding whipped cream to our custard gets air into the base, making a lighter, easily scoopable final product.

4 egg yolks

1⁄2 cup sugar

1 1⁄2 cups heavy cream

2 teaspoons vanilla, optional

For the custard, whisk yolks and sugar together until well combined; reserve. Heat 1 cup cream to a simmer in a heavy-bottomed saucepan over medium heat; remove from heat. Temper the cream into the yolk mixture a tablespoon at a time until 5 ounces are mixed in. Whisk yolk/cream mixture back into remaining warm cream. Heat gently, stirring constantly, until slightly thickened, about 2 1⁄2 minutes. Whisk in optional vanilla, then remove from heat; chill in freezer until very cold but not frozen.

While custard chills, whip remaining 1⁄2 cup cream to soft peaks.

When custard is cold, fold in whipped cream with a spatula.

Makes about 1 pint (4 servings). Nutrition information per serving: 458 calories, 37 g fat, 22 g saturated fat, 286 mg cholesterol, 28 g carbohydrates, 28 g sugar, 5 g protein, 33 mg sodium, 0 g fiber

Variations on a theme

For a lighter ice cream, make custard with 1 cup whole milk or half-and-half before proceeding with the folding in of the whipped cream.

Instead of making custard, substitute one can of sweetened condensed milk. Chill and fold in whipped cream as above.

Add as much flavoring ingredients as you like, and taste as you go: chocolate chips or syrup, macerated berries, etc.