Gently heat your milk. My preferred method of choice is slowly heating it in the microwave until it is just warm (around 110 degrees max). Pour your milk into a mixing bowl for your dough and add in the yeast. Stir mixture and let sit until foamy (about 5 minutes).
Add in the flour, sugar, salt, butter, cardamom, and yeasty milk (from the previous step). Mix with a large spoon and then your hands until it forms a dough (about 3 minutes). Continue to knead for a couple more minutes until the dough becomes smooth and shiny.
Flatten the dough out into a rectangular block about a half an inch thick. This step is merely to allow the dough to set up, the actual dimensions are not yet relevant. Score your dough a few times with a knife with shallow cuts to allow it to expand. Cover your sheet with plastic wrap (or damp towel) and store in the fridge for a couple hours to chill.
Prepare the filling. Grab a medium sized bowl and add all your ingredients together (butter, sugar, cardamom, and salt). Mix thoroughly with a fork until the mixture becomes homogenized and then stop mixing, no need to overmix.
Take your dough out of the refrigerator and place it on a lightly floured surface. Roll the dough out to a rectangle about 4x18 inches and about ⅛ inch thick.
Prepare your baking sheet with your choice of parchment paper or silicone mats (I have heard parchment paper leads to crunchier bottoms, but I have not tested between both methods).
Now is the time to top your dough with your filling you made earlier. Place dollops of the filling across the dough and smooth it out to an even layer all over the dough.
Now is time to make some layers! Fold the top third of the long side of the dough over the middle third and then fold the bottom third on top of that. This will create those delicious layers of cardamom throughout the dough.
Roll out the dough again so that it measured about 4x12 inches. Try not to roll out too much of the filling but just know it will be ok if some filling comes out.
Using a pizza cutter cut your 4x12 inch dough into 4 1x12 inch rectangles. Next, one at a time cut a line down the middle of your 1x12 inch rectangle up to about 11 inches up the dough. Now pick up the dough by the connected end and with your other hand grab the loose ends. Twist the loose ends of the dough a few times and then with your hands holding the loose ends, wrap around your fingers holding the connected end two times and then bring the loose ends up through the bottom of the dough to tie it off. This takes a bit of practice but even questionable looking rolls turn out great in the end. After forming each bun, place them on your baking sheet with some spacing between them to allow them to grow.
Cover and let proof for about an hour or until puffed up. Preheat your oven to 450℉ during this time.
In a small bowl, beat your egg with a splash of water until frothy. Next combine your ground cardamom and sugar. Next Brush your buns with the egg mixture and then sprinkle on the cardamom and sugar mixture to top. (This is the secret to a crispy topping).
Bake buns in the oven at the high heat for about 8 minutes and then lower the temperature to 375℉ and continue baking for an additional 10-12 minutes until the buns are a nice golden brown.
The hardest part now. Wait until the buns have had a chance to cool before eating to let the crispy sugary coating solidify. Now, go enjoy your delicious treats, you deserve it!