Rhubarb crisp is a dessert in the crisp family which features rhubarb, a tangy herb which is usually treated as a fruit, since it is used primarily in desserts. On its own, rhubarb has a sour, sharp flavor, but when served with the streusel topping used to make crisps, the flavor of the rhubarb mellows, and the result is a sweet dish with a hint of a bite. Rhubarb is also famously used in strawberry rhubarb pie.
Crisps are extremely simple fruit desserts, perhaps the easiest fruit desserts to make beyond simply eating fruit plain. To make a crisp, cooks toss a layer of sliced fruit into the bottom of a buttered baking pan, and then top the fruit with a streusel mixture before baking the dessert until the streusel browns and the fruit softens. As the dessert cooks, the streusel also becomes very crunchy and crisp, which explains the name.
Rhubarb looks sort of like celery, with tall reddish crunchy stalks, although the leaves are large, crinkled, and arrow-shaped, rather than small and feathery like those of celery. When selecting rhubarb for baking, firm, brightly colored stalks should be chosen. Many producers do not trim the leaves, as rhubarb stays fresher longer with the leaves on, but the leaves are not edible, and they should be trimmed away.
While the rhubarb can be thrown into the pan as-is, some cooks like to toss the chopped rhubarb with lemon juice, a little bit of sugar, and some flour or cornstarch to thicken the juices which will leach out as the rhubarb cooks. The streusel topping includes equal parts flour, sugar, and butter, with added spices to taste such as cinnamon, nutmeg, ginger, or allspice, among others. The butter can either be softened and cut into the dry ingredients until a crumbly mixture is formed, or melted and stirred in with the dry ingredients.
This crisp doesn't have to stop with rhubarb. Cooks can make strawberry rhubarb crisp or raspberry rhubarb crisp, for example, making a naturally sweeter dish with these berries. Other fruits like apples are also not uncommon additions to rhubarb desserts. Rhubarb crisp can also be served with ice cream or whipped cream to enhance the flavor, and it may be eaten hot or cold, although many people prefer hot rhubarb crisp. Rhubarb crisp can also be prepared, frozen, and baked at a later time so that the taste of rhubarb can be enjoyed when this herb is not in season.