In a 12-inch nonstick skillet, bring 1 cup water and the butter to a boil over high heat. Add the snap peas; cover, and cook until bright green, about 2 minutes. Remove the lid; reduce the heat to medium. Continue cooking, tossing occasionally, until the peas are crisp-tender and the water has evaporated, 2 to 4 minutes. Remove from the heat. Toss with the mint and season with salt and pepper.