Preheat oven to 350 F. Prepare 3 x 8" cake pans with parchment paper. In bowl of standing mixer, sift all dry ingredients. Add all remaining ingredients to bowl with the dry ingredients and with paddle attachment on mixer, mix for 2 minutes on medium speed and pour into prepared pans. Batter will be liquidy.
Bake for 20 minutes and rotate pans in oven (if not cooked in convection oven). Cakes are done when toothpick or skewer comes clean, approximately 35 minutes.
Place marshmallows on cookie sheet lined with parchment paper. Place in the oven, and broil marshmallows until nice and brown. Keep an eye on them as they burn very quickly. Combine butter and icing sugar in standing mixer fitted with paddle attachment, on low until blended (about 1 minute). Add vanilla and mix on high for about 3 minutes. Add marshmallow cream and toasted marshmallows, and mix on lowest setting for about 1 minute.
Malted Belgian Chocolate Frosting
In a bowl of a standing mixer fitted with paddle attachment, combine the powdered sugar and butter and beat on low speed for about 1 minute. Add vanilla and malt powder, and beat on low until well combined. Add the melted chocolate and beat on medium speed until smooth (about 2 minutes). Add whipping cream and beat on med-high speed for another minute. Best used right away.
*The malted chocolate frosting isn't my favorite, It isn't bad though. I'm a lover of freshly made Swiss meringue or French butter cream, nothing compares to those two!
In small saucepan over medium high heat, add blueberries, sugar and lemon juice. Mash blueberries until only a few remain whole. Heat and stir until boiling. Remove from heat and allow to cool and thicken. Set aside.
In a large bowl, whisk together flour, sugar, baking powder, and salt. Beat in greek yogurt, eggs, vanilla, milk and melted butter until fully incorporated.
Spray doughnut pan with non-stick spray, filling each cavity with ¼-1/3 cup doughnut batter. Dollop two to three tsp of blueberry jam on top doughnut batter in each doughnut pan cavity. Using a knife swirl the jam into the doughnut batter. Bake in oven for 9 minutes, or until light golden brown.
In small bowl, whisk together powdered sugar, lemon zest, milk and vanilla bean caviar until sugar is dissolved and mixture is runny. Dunk tops of doughnuts into glaze and turn right side up to set. Serve while still slightly warm.