Preheat oven to 350℉ degrees. Prep your pan with nonstick spray. I used a 8"x10" pan, but you can use a 9"x13", you will just cook it for a shorter amount of time.
In a large bowl, mix together the sugars, flour, chai spice mix, melted butter, and salt.
Once combined remove 1 cup of this mixture and set aside. This will become the streusel topping for the coffee cake.
In a separate container mix together the buttermilk, egg, baking powder, and baking soda.
Add the buttermilk mixture to the bowl with the flour/sugar mixture and mix until combined.
Pour this mixture into a baking dish. I used an 8″x 10″.
Sprinkle the 1 cup mixture you had set aside on top for the crumble.
Bake for 45 to 50 minutes.