Separate the egg whites from the egg yolks. (Transfer the egg yolks to a separate bowl and set aside).
Place the egg whites into a stand mixer bowl fitted with a whisk attachment.
Start the mixer and when the egg whites become foamy, add in the cream of tartar.
Gradually add in the sugar and whip until stiff and shiny peaks.
Dump the almond flour into the meringue and fold with a spatula until the almond flour is incorporated.
Divide the mixture evenly into two round 6" pans lined with parchment paper.
Bake at 350°F/177°C for 20-25 minutes, until lightly golden in colour.
Remove from the oven and let cakes cool on a rack.
Make the golden cream:
Similar to making a custard, whisk together the egg yolks, sugar, salt, milk powder and vanilla extract into a glass bowl.
Warm heavy whipping cream in a small saucepan over medium heat.
While whisking the egg yolk mixture, pour the warm cream into the egg yolks and transfer back into the saucepan.
Continue to whisk over medium heat until the mixture thickens, about 8-10 minutes.
Remove from heat and stir in 1 tablespoon of butter.
Completely chill the cream mixture in the fridge for at least 6-8 hours.
Pour the chilled cream and whip with a wire whisk (in a stand mixer) until lightens up a little. (Don't worry if the mixture doesn't completely whip up, we're just looking for it to be a little lighter).
Assemble:
Slice the almond cake in half.
Spread about ¼ C of whipped golden cream over the cake with an offset spatula.
Place another layer of cake on top of the cream.
Spread another layer of golden cream and cover the edges of the cake with the cream.
Coat the top and sides of the cake with toasted almond flakes.
Repeat with the second cake, unless making 1 x 4-layered 6" cake.
Chill the cake in the freezer for at least 6-8 hours before serving.