Warm milk to around 110 degrees F. I like to do this by placing milk in a microwave safe bowl and microwaving it for 40-45 seconds. It should be like warm bath water. Transfer warm milk to the bowl of a stand mixer mixer and sprinkle yeast on top. Add in sugar, egg, egg yolk and melted butter. Mix until well combined. Next stir in flour and salt with a wooden spoon until a dough begins to form.
Place dough hook on stand mixer and knead dough on medium speed for 8 minutes. Dough should form into a nice ball and be slightly sticky. If you do not have a stand mixer handy, you can use your hands to knead the dough for 8-10 minutes on a well-floured surface.
Transfer dough ball to a large bowl generously coated in oil, cover with plastic wrap and a warm towel. Allow dough to rise for 1 hour to 1 ½ hours, or until doubled in size. This may more or less time depending the humidity and temperature in your home.
Another tip for rising dough is to heat your oven to 175 degrees F, then turn the oven off and place the covered bowl of dough in the warm oven to rise for 45 mins to an hour. This is the method I use in the colder months.
While dough is rising, prepare spiced apple mixture. Chop two medium sized apples into cubes. Heat two tablespoons of butter over medium high heat and add apples, brown sugar, cinnamon, nutmeg, cloves and cardamom. Bring to a boil then reduce heat to medium and simmer until apples are softened, about 5-7 minutes. Once apples are softened, remove from heat and allow them to cool to room temperature.
After dough has doubled in size, transfer dough to a well-floured surface and roll out into a 14x9 inch rectangle. Spread softened butter over dough, leaving a ¼ inch margin at the far side of the dough.
In a small bowl, whisk together brown sugar, cinnamon and cardamom. Use your hands to sprinkle mixture over the buttered dough, then rub the brown sugar mixture into the butter. Evenly spread apple mixture on top of sugar layer. I recommend using a slotted spoon so that all of the juice from the apples doesn't get into the rolls.
Tightly roll dough into a log, starting from the 9-inch side and place seam side down making sure to seal the edges of the dough as best you can. You will probably need to cut off about an inch off the ends of the dough as they will not have much filling in them.
Cut into 1-inch sections with a serrated knife or floss. You should get 9 large pieces.
Place cinnamon rolls in a greased 9x9 inch baking pan or round 9-inch pie dish. Cover with plastic wrap and a warm towel and let rise again for 30-45 minutes.
Preheat oven to 350 degrees F. Remove plastic wrap and towel and bake cinnamon rolls for 20-25 minutes or until they just start to turn golden around the edges. You don't want to overbake them, so they remain soft in the middle. Allow rolls to cool for 5-10 minutes before frosting.