How to Make Cold Foam at Home

Before you start

Cold foam is milk frothed without heat until it turns into a dense, velvety layer that floats on iced coffee. It does the job of a cappuccino's foam in a cold drink: a creamy first sip without diluting the coffee underneath. The surprising part is that the leanest milk foams best. Milk proteins build the bubbles, and fat weakens them, so nonfat milk makes the stiffest, longest-lasting foam.

That sets up the main choice. Nonfat milk gives a tall, airy foam with a light taste. Adding a little cream or using a sweet cream base tastes richer but foams lower and softer. Whatever you use must be very cold, straight from the fridge, and you should froth it in a tall, narrow container so the whisk pulls in air without splashing.

Ingredients

• 60 ml (2 oz) cold nonfat (skim) milk — the coldest milk you have
• 10 ml (2 tsp) vanilla syrup or simple syrup — optional; sugar also steadies the foam
• 15 ml (1 tbsp) heavy cream — optional, for a richer, softer foam
• 1 iced coffee or cold brew — to serve, about 300 ml

Method

1. Pour the cold milk, syrup and cream, if using, into a tall narrow cup. The liquid should come no more than a third of the way up, since it will roughly double in volume.
2. Frother method: submerge the whisk just below the surface and switch it on. Hold it there for 10 seconds to pull in air, then lower it and move it gently up and down for another 15 to 20 seconds, until the foam is thick, glossy and pours slowly like melted ice cream.
3. French press method: pour the milk into a clean press, put the lid on and pump the plunger quickly in short strokes 30 to 40 times, until the foam reaches about double the starting level.
4. Jar method: fill a jar no more than a third full, seal it tightly and shake hard for 45 to 60 seconds. This gives a looser foam with larger bubbles but works without any tools.
5. Tap the cup on the counter once or twice and swirl it to pop large bubbles and smooth the texture.
6. Pour the foam slowly over your iced coffee, or spoon it on, so it rests on top. Use it within a few minutes.

Tips for success

• Chill the frothing cup or French press for a few minutes in the freezer. Every degree colder helps the foam hold.
• Add flavor before frothing, not after. Stirring syrup into finished foam knocks out the air.
• If your iced coffee is very full of ice, leave about 3 cm of space at the top so the foam has room to sit instead of sliding over the rim.

Substitutions

Nonfat milk

2% milk foams well but a little lower. Whole milk gives a soft, short-lived foam. A two-to-one mix of cream and milk with syrup makes a rich sweet cream foam that is dense rather than tall.

Dairy milk

Barista-style oat milk foams cold reasonably well thanks to added stabilizers. Regular almond and rice milks rarely hold a cold foam for more than a minute or two.

Vanilla syrup

Any flavored syrup works, from caramel to brown sugar. Maple syrup adds a pleasant flavor and helps stability. A pinch of cocoa or cinnamon can be frothed in too.

Variations

Salted honey cold foam

Froth the milk with 10 ml honey thinned with a few drops of hot water and a pinch of salt.

Chocolate cold foam

Add 1 tsp cocoa powder and 10 ml simple syrup before frothing.

Troubleshooting

The milk barely foams

The milk was not cold enough, the container is too wide, or there is too much fat. Use very cold skim milk in a narrow cup and keep the whisk near the surface at first.

The foam is bubbly and collapses fast

Large bubbles form when the frother runs too long at the surface. Draw air in for only 10 seconds, then sink the whisk to break the bubbles into a fine microfoam.

The foam sinks into the drink

It was too thin, or poured from high up. Froth a little longer, and pour from just above the surface or spoon it on.

Storage

Cold foam does not keep. It starts to separate within 5 to 10 minutes, so froth it right before serving. Return the milk to the fridge promptly, and do not leave dairy out for more than 2 hours.