MAPLE CRUNCH LAYER CAKE

Steps:

• For candy:
• Line baking sheet with aluminum foil; brush foil with vegetable oil. Stir maple syrup, sugar, and apple cider vinegar in heavy medium saucepan until sugar is moistened. Attach candy thermometer. Without stirring, bring mixture to boil over medium-high heat and boil until temperature registers 300°F, occasionally brushing down pan sides with wet pastry brush and swirling pan, about 7 minutes. Remove pan from heat; mix in baking soda, then nuts (mixture will foam up).
• Immediately pour maple candy out onto prepared baking sheet and spread to even 1/2-inch thickness (candy begins to firm quickly). Let stand until candy hardens, at least 30 minutes. (Can be made 1 day ahead. Cover baking sheet tightly with plastic wrap and store candy at room temperature.)
• For cake:
• Preheat oven to 350°F. Spray two 8-inch-diameter cake pans with 2-inch-high sides with nonstick spray. Line pan bottoms with parchment paper; spray parchment. Whisk flour, baking powder, baking soda, salt, and cinnamon in medium bowl to blend.
• Using electric mixer, beat butter in large bowl until fluffy. Add golden brown sugar and beat until blended and fluffy. Gradually beat in maple syrup (batter may look curdled). Beat in eggs 1 at a time, then vanilla extract. Beat in dry ingredients in 3 additions alternately with buttermilk in 2 additions. Divide batter between prepared pans.
• Bake cakes until tester inserted into center comes out clean, about 30 minutes. Cool cakes 5 minutes. Turn cakes out onto racks, peel off parchment paper, and cool cakes completely. (Can be made 1 day ahead. Wrap tightly; store at room temperature.)
• For buttercream:
• Bring maple syrup to boil in small saucepan. Meanwhile, using electric mixer, beat egg whites in large bowl until stiff peaks form. Without letting hot maple syrup touch beaters, pour 1/4 cup syrup into egg whites, beating to blend. Gradually beat in remaining hot maple syrup. Continue to beat until whites are stiff and cool, about 15 minutes. Add butter, 1 slice at a time, beating to blend after each addition (buttercream may deflate and separate; keep beating until smooth again).
• Chop enough maple candy into 1/4-inch pieces to measure 1 cup; wrap remaining maple candy tightly in plastic. Place 1 cake layer on platter. Spread 1 cup buttercream over cake. Sprinkle with 1 cup maple candy pieces; press candy lightly to adhere. Top with second cake layer. Spread remaining buttercream smoothly over top and sides of cake. (Can be made 1 day ahead. Cover with cake dome; chill. Bring to room temperature before continuing.)
• Chop enough of remaining maple candy into 1/4-inch pieces to measure 2 cups. Mince enough maple candy to measure 2 tablespoons. Press 1/4-inch pieces onto sides of cake. Sprinkle minced maple candy on top edge. Serve cake within 2 hours.