In a large bowl, beat the eggs, sugar and vanilla until thick and lemon-colored, about 4 minutes. Combine the flour, baking powder and salt; add to egg mixture. Beat on low speed just until combined. Beat in milk and butter.
Pour into a greased 13-in. x 9-in. baking pan. Bake at 350° for 30-35 minutes or until a toothpick inserted near the center comes out clean. Cool on a wire rack. Cut into squares. Cover and freeze overnight.
For frosting, in a small bowl, beat the confectioners' sugar, milk, vanilla and salt until smooth. Frost the top and sides of frozen cake squares; roll in peanuts. Place on wire racks to set. Yield: 2 dozen.