In a large bowl, cream the butter and sugar until light and fluffy. Beat in the eggs until well blended. Beat in the syrup. Combine the flour, baking powder and salt; add to the creamed mixture alternately with milk, beating well after each addition. Fold in nuts.
Pour into two greased and floured 8-in. round baking pans. Bake at 350° for 20-25 minutes or until a toothpick inserted in the center comes out clean. Cool for 10 minutes before removing from pans to wire racks to cool completely.
In a heavy large saucepan, combine the frosting ingredients. With a portable mixer, beat on low speed for 1 minute. Continue beating over low heat until frosting reaches 160°, about 8-10 minutes.
Pour into the bowl of a heavy-duty stand mixer. Beat on high until stiff peaks form, about 7 minutes. Frost between layers and over top and sides of cake.