In a medium bowl, combine the flour, baking powder, baking soda, cardamom, salt, and sugar.

In another bowl, beat the egg yolks, vanilla and buttermilk with a whisk or handheld mixer until frothy. Stir the dry ingredients into the wet ingredients just to combine.

In another bowl, beat the egg whites until frothy and stiff peaks form. Gently fold the egg whites into the batter.

Rub a little of the unsalted butter into each indentation of a well-heated aebleskivers pan. With a paper towel, remove excess butter. Place about 1 tablespoon batter in each indentation, top with about 1⁄2 teaspoon of preserves of choice, and add another tablespoon of batter on top. Cook until the sides are set and bottom is golden brown, about 2 minutes.

Using two wooden skewers, carefully turn the aebleskivers over to cook the other side. Cook for 1 to 2 minutes more. Transfer to a platter, dust with powdered sugar, and serve hot. Repeat with remaining batter.

Makes about 3 dozen.