These compact baby lettuce heads are sometimes called French romaine. I've heard people say Little Gem is a cross between butter and romaine, but more accurately, it's "like" a cross between butter and romaine—actually classified as an heirloom romaine.
The leaves are tender and sweet, yet crisp. Their bumpy, romaine-like surface makes Little Gem a good candidate for creamy dressings. Unlike romaine, the lettuce is never stringy or tough. It is, however, sturdy enough to cook, like an escarole.
The little heads make portion planning simple. One small one is the perfect single serving. A medium size head is usually just right for two. They're quite good-looking as a plated salad and fun to serve quartered or halved with a buttermilk blue cheese dressing.
here's a nice Little Gem Salad idea from smallfarms.com.
Their size and shape makes them perfect for lettuce wrap recipes like this one.
Here's a recipe for grilled Little Gems.
So many recipes on the web are British, I have to think that this lettuce has been popular in Europe for ages.