Prepare Dough: Warm milk and melt butter in it. Mix with dry yeast, half an egg, sugar, salt, cardamom, wheat flour, and baking powder to form an elastic dough. Let it rise until doubled in size.
Shape and Bake Buns: Divide the dough into 6 parts, let rise again until doubled. Glaze with egg and milk mixture. Bake in air fryer at 190 degrees Celsius for 10-12 minutes. Allow to cool.
Make Brunsviger Glaze: Combine brown sugar, butter, water, cinnamon, cardamom, and a pinch of salt in air fryer basket. Cook at 200 degrees Celsius for 10 minutes.
Prepare Cake Cream: Heat cream, milk, egg, egg yolks, sugar, vanilla pod, and cornstarch until thickened. Cool and whisk until smooth.
Cook Bacon: Place bacon slices in air fryer. Cook at 180 degrees Celsius for 10 minutes until crispy.
Whip Cream: Whip 0.5 liters of cream until stiff peaks form.
Assemble Buns: Cut off the top of each bun and hollow out slightly. Dip the top in Brunsviger glaze. Fill with cake cream and glaze. Pipe whipped cream around the edge, replace the top, and garnish with bacon.