To make cold foam in a jar, pour half & half and sweetener into a large jar with a tight lid. Shake vigorously until it doubles in volume.
The goal is to get tiny, uniform bubbles that won’t even look like bubbles since that’s what creates the smooth texture. The French press does a better job of doing this than the handheld milk frother.
The French press makes better cold foam but it’s a bit of a chore to clean. The handheld milk frother is much easier to clean than a French press but the cold foam isn’t as smooth since there are bigger bubbles. But they both taste great and adds velvety foam to your iced drink.
Don’t overfill the French press. The cold foam will double or triple in volume as air is pumped in, so keep that in mind when you pour the half & half into the French press.
Don’t underfill the French press. The strainer needs to be submerged in the half & half so that the air can be pumped into it.