Position rack in center of oven and preheat to 325°F. Butter two 8-inch-diameter cake pans with 2-inch-high sides. Line bottom of pans with parchment paper; butter parchment. Dust pans with flour; tap out excess. Sift 3 cups flour, baking powder, and salt into medium bowl. Using electric mixer, beat butter and shortening in large bowl until light and fluffy. Add maple syrup and beat until smooth, about 3 minutes. Add egg yolks and egg 1 at a time, beating until well blended after each addition. Beat in flour mixture in 3 additions alternately with milk in 2 additions. Divide batter equally between prepared pans (about 3 1/2 cups for each); smooth tops.
Bake cakes until tester inserted into center comes out clean, 50 to 55 minutes. Cool cakes in pans on racks 20 minutes. Run small knife around sides of cakes to loosen. Invert cakes onto racks; remove parchment. Cool cakes completely.
Over medium high heat in heavy saucepan, melt butter. Watch butter carefully and let it bubble. It will begin to show brown bits in the bottom of the pan and you will start to smell the aroma of the nutty buttery goodness. Once it has browned, immediately remove from heat. In a standing mixer fitted with a whisk, mix together sugar and butter. Mix on low speed until well blended and then increase speed to medium and beat for another 3 minutes. Add syrup and cream and continue to beat on medium speed for 1 minute more, adding more cream if needed for spreading consistency.
Using serrated knife, trim off domed top of each cake layer, creating flat surface. Place 1 cake layer, trimmed side up, on platter. Spoon 1 cup frosting in dollops over top of cake layer; spread evenly to edges. Top with second cake layer, trimmed side down. Spread remaining frosting evenly over top and sides of cake.