Note: If making your own walnut flour, pulse the walnuts a few times, measure out 1/2 cup, then pulse again mixed with the flour. Otherwise it will turn to walnut butter.
Preheat oven to 350F. Grease and flour three 6" cake rounds and line with parchment.
In a medium bowl, whisk flour, walnut flour, baking powder,and salt until well combined. Set aside.
Using a stand mixer fitted with a paddle attachment, cream butter and sugar on med-high until pale and fluffy (approx 3mins). Reduce speed and add eggs one at a time fully incorporating after each addition. Add honey and vanilla and blend well.
Alternate adding flour mixture and milk mixture, beginning and ending with flour (3 additions of flour and 2 of milk). Fully incorporating after each addition.
Bake for about 25-30 mins or until a toothpick inserted into the center comes out mostly clean.
Place cakes on wire rack to cool for 10mins then turn out onto wire rack. Allow cakes to cool completely.
Honey Cinnamon Swiss Meringue Buttercream:
Place egg whites and sugar into the bowl of a stand mixer, whisk until combined.*
Place bowl over a pot with about 1" of simmering water. Whisk constantly until the mixture is hot and no longer grainy to the touch (about 3mins). Or registers 160F on a candy thermometer.
Place bowl on your stand mixer and whisk on med-high until the meringue is stiff and cooled (the bowl is no longer warm to the touch (about 5-10mins)).
Switch to paddle attachment. Slowly add cubed butter and mix until smooth.** Add honey and cinnamon and whip until fluffy.
Honey Glazed Walnuts:
Prepare as per recipe. Cool completely. Pick out any pretty whole pieces to adorn the bottom of the cake. Chop enough of the remiander to measure out 1/2 cup chopped walnuts.
Place one layer of cake on a cake stand or serving plate. Top with approximately 2/3 cup of buttercream, spread evenly. Sprinkle 1/4 cup chopped honey walnuts over top. Repeat with remaining layers.
Frost and smooth the outside with a thin crumb coat. Chill for 20mins.
Frost and smooth the outside of the cake. Pipe a rope border along the top using a small star tip (I used #32).
Place honey glazed walnuts along the bottom as well as some on the top with some pieces of honeycomb if desired. Drizzle with honey.
* Wipe your mixer bowl and whisk down with lemon juice or vinegar to make sure it is completely grease free and make sure there is no trace of yolk in your whites or your meringue will not stiffen. ** The buttercream may look like it's curdled at some point. Keep mixing until it is completely smooth. If it looks soupy, place it in the fridge for 20mins and rewhip.Honey Walnuts recipe from Melanie at Garnish & Glaze.