Make the Brown Sugar Nutmeg Cake:

1. Pre-heat oven to 350°F. Grease and flour 3 8-inch cake pans and put aside.
2. In a blending bowl, whisk in combination the flour, baking powder, salt, cinnamon, and nutmeg. Put aside.
3. Within the bowl of a stand mixer, position the butter, brown sugar, and granulated sugar. Combine on medium till gentle and fluffy, 2 to three mins. Flip the mixer to medium-low and upload the vanilla. Upload within the eggs and egg yolk, one after the other, and blend till integrated. Upload the oil and blend till blended (if the batter breaks, upload about ½ cup of the flour combination and blend till easy).
4. Prevent the mixer and scrape down the bowl. Upload the flour combination in two batches, alternating with the milk – beginning and finishing with the flour combination. Combine on medium for not more than 30 seconds, or till easy.
5. Flippantly divide the batter between the ready pans. Bake for twenty-four to 26 mins or till a toothpick inserted into the middle of the muffins comes out blank. Cool on a cord rack for 10 to twenty mins earlier than doing away with the muffins from their pans. Permit muffins to fully cool earlier than filling and frosting.

Make the Hazelnut Praline:

1. Position the sugar, water, and cream of tartar in a saucepan. Warmth over top and convey to a boil. Proceed to cook dinner the sugar combination till it turns a medium amber shade (like making caramel sauce), and in an instant take away from the warmth.
2. Straight away stir within the hazelnuts, cinnamon, and salt. Briefly and sparsely (it’ll be extremely popular!) unfold the mix onto a silicone baking mat or piece of parchment paper. Permit to fully cool.
3. As soon as cool, smash the brittle into items in order that they are compatible in a meals processor. With a meals processor, grind the brittle right into a powder.

Make the Hazelnut Buttercream:

1. Position the egg whites and sugar within the bowl of an electrical mixer. Gently whisk till blended.
2. Position blending bowl over a pan of simmering water to create a double-boiler.  Whisking repeatedly, warmth the egg combination till it registers 160°F on a sweet thermometer. Sparsely switch the bowl again to the stand mixer.
3. The usage of the whisk attachment, whip the egg combination on top for 8 to ten mins till stiff, shiny peaks and the out of doors of the blending bowl returns to room temperature.
4. Transfer to the paddle attachment.  With the mixer on low, slowly upload the butter (a pair tablespoons at a time) and blend till integrated.
5. Upload vanilla.  Whip on medium till silky easy, about 3 to five mins.
6. Take away 2 ½ cups of buttercream to combine with the praline powder. Reserve the remainder buttercream to frost the cake.

Compile the Cake:

1. Position one layer of cake on a cake board or serving dish. Unfold on about 1 cup of the hazelnut praline buttercream with an offset spatula till easy. Most sensible the following layer of cake and repeat. Position the general layer of cake and peak and crumb coat the cake in a skinny layer of the remainder hazelnut praline buttercream. Kick back the cake within the fridge for quarter-hour.
2. Tint the remainder buttercream your shade of selection (if desired). Position a big dollop of buttercream at the peak of the chilled cake. Unfold out the buttercream with an offset spatula till easy. For the edges of the cake, use an offset spatula to unfold somewhat of buttercream across the backside edges (about 1-inch from the ground).
3. To embellish, rating the cake with the threshold of an icing smoother or the aspect of a spatula to make vertical strains each and every 2 to 3-inched across the cake. Fill a piping bag fitted with a medium big name tip (like Wilton 1B) with buttercream. Beginning on the backside of the cake, pipe massive swags across the cake. The tops of the swags must get started and finish on the vertical marks scored at the cake. Proceed up the edges of the cake, piping the swages round, till the cake is roofed.
4. Most sensible with Nutcracker paper toppers, if desired.
5. Serve at room temperature. Refrigerate any leftovers.