In a mixing bowl, cream the butter and sugar together until smooth.
Add in the eggs, one at a time. Beat until thoroughly incorporated.
Add in the flour a little at a time. Mix well.
Lastly, add in the cardamom and vanilla extract, and mix until incorporated.
Preheat the krumkaker iron. Once heated, drop a heaping tbsp. of the batter into the center of the ornate pattern on the iron. Clamp the lid down.
When the iron light indicates the krumkaker is done, lift the lid. Place the cone on on side of the flat krumkaker. Use a fork to begin forming the krumkaker around the cone while you spin the cone with the other hand.
Keep the krumkaker on the cone for at least 10 seconds or so until it starts to harden. Then, remove the krumkaker from the cone and let it rest on a towel, seam side down, to cool more and firm up.
Once more firm, place the krumkaker on a cooling rack to finish cooling. You'll get the hang of the timing. Just be patient and expect the first few to break. Perfect for snacking on!
Let the krumkaker cool completely before serving. Store them in a hard-sided, sealed container to protect them from breaking and to keep them crisp.
Enjoy the krumkaker plain or filled with whipped cream and berries!