Chai Latte Cookies - the recipe as requested

Here's the recipe for another of the various Baked Goodies that I'm taking to my medieval event that I leave for on Sunday, to camp out with 5000 other history geeks, ren-fair junkies, and anachronist nerds...

Chai Latte Shortbread Cookies

5 cups + a bit sifted all purpose flour
2 teaspoons baking powder
1 cup (aprx 12 oz) plain greek yogurt
1/4 cup butter (1 stick) softened to room temperature
1 1/2 cups granulated sugar
2 teaspoons vanilla extract
1/2 teaspoon ground nutmeg
1/4 teaspoon ground green cardamom
1/4 teaspoon ground white cardamom
1/2 teaspoon ground cinnamon
1/4 teaspoon ground crystalized ginger
1/4 teaspoon ground clove
1/4 teaspoon ground star anise
1/8 teaspoon ground black peppercorn
1/8 teaspoon ground bay leaf
pinch of salt (this can be omitted if you use salted butter, but needs to be included if you use unsalted butter)
2 eggs

(The Individual spices listed can be substituted for your favorite Chai blend as long as it contains only spices.   In the OKC area, I get my Chai spice blend ready to grind from Savory Spice Shop on Western, 2 oz at a time.  I ground up the entire tube of Chai spices to use for this recipe, then added nutmeg and extra cardamom. You will probably want to adjust the amounts to taste, since these are approximate.)

Grind togther all spices except vanilla extract and salt (if using) - a small coffee grinder works great to get everything to the same consistency.

Mix Chai spices and sugar, then cream together with softened butter, vanilla, eggs, and yogurt until smooth. 

Add salt and baking powder, stirring until evenly distributed.

Begin mixing in flour a little at a time, until dough is no longer sticky, and has become somewhat stiff.  Refrigerate for 4 to 24 hours to allow dough to rest.
Roll out on lightly floured board to 1/4 inch thickness and cut into rounds (or use your favorite cookie cutter!)
Bake for 10 to 12 minutes at 325F on parchment lined cookie sheets - bottom edges should just begin to turn darker brown.