These familiar round, red radishes belong to the Red Globe variety. They should be plump, firm, smooth, and free of cracks and blemishes. If you plan on serving radishes raw as a snack, buy them with the leaves still attached; they should be bright green and fresh. Smaller radishes are usually sweeter; larger ones can be sharper and more peppery (good in salads). Radishes are also available in plastic bags, without their tops.
Place all radishes in a perforated plastic bag in the crisper. Those purchased with tops removed can be kept up to a week. Radishes with leaves on should be used within a day or so because the greens don't stay fresh very long.
Rinse before using: Place radishes in a bowl of cold water; swish around. Drain, and dry on paper towels. Before rinsing radishes with leafy tops, trim greens down to about one inch. Then with the tip of a sharp knife, scrape around the base of the greens, and pinch off the tiny root, if desired.
Soak radishes in ice water for about 20 minutes. Drain; pat dry. Arrange on platter. Place softened butter in a small bowl, coarse salt on a plate. Dip radishes first in butter, then in salt; they're ready to eat.