Heat buttermilk for 40 seconds in the microwave. I like to do this in a liquid measuring cup. Add the yeast and sugar and mix.
Next, add butter to a large bowl. Pour sugar/buttermilk mixture into the bowl. Whisk with a hand mixer or stand mixer until the butter has broken down.
Add the egg and salt. Mix until incorporated.
Lastly, add the flour and combine until a dough forms.
Empty the dough onto a floured surface. Knead for 3 minutes and let it rise for an hour. You can also knead the dough in a stand mixer for the same amount of time. If the dough still seems wet, add a tablespoon of flour at a time until it doesn’t stick to your hands.
Cover with a wet towel or aluminum foil and let the dough rise for 1 hour until it doubles in size.
While the dough is rising, make the spice mixture for the filling. Combine cinnamon, cardamom, ginger, star anise, and earl grey tea in a bowl. Mix and set aside.
Once the dough is done proofing, punch out the air. Then roll it out into a 12x12 inch square. Smear the top of the dough with butter. Top with brown sugar and the spice mixture.
Roll into a log and cut into 9 equal pieces. Cut the log into 3 equal pieces and then divide each piece into 3 equal pieces.
Place the cinnamon rolls into a greased 9x9 pan. Let the dough rise for an hour.
Preheat the oven to 350 degrees F (177 degrees C).
After the last proof (rise), bake for 20-25 minutes uncovered until the edges are light brown.
While the cinnamon rolls are baking, combine all the ingredients for the glaze and mix. Set aside.
Cool for 5-10 minutes before adding the glaze.