Combine peppers and 1 cup hot water; let stand 10 minutes. Drain peppers, reserving 1/2 cup water.
Process peppers and reserved water in a blender until smooth, stopping to scrape down sides.
Peel potatoes, and cut into 1-inch cubes. Cook in boiling water to cover 20 to 25 minutes or until tender; drain and place in a large mixing bowl. Add pepper puree, beer, and salt; beat at medium speed with an electric mixer until smooth and fluffy (do not overbeat).