Heat the milk in a small pan until it starts to bubble.
Add the buttermilk and transfer the liquid to the bowl of a stand mixer.
Mix in the yeast and sugar, let sit for 5 minutes.
Add the flour, baking soda, salt and pie spice.
Mix on low speed until the dough comes together, it'll be quite wet and sticky. About 5 minutes.
Take the bowl off the machine and cover with a dry towel or plastic wrap and let it rest for 1 hour.
Add about 2 inches deep of oil to a deep sided pan and heat to 375 degrees on a thermometer.
Dust your work surface with flour and dump the dough out onto the flour.
Add some more flour to the top of the dough and gently fold it into a ball shape.
Roll the dough out to a flat sheet about half an inch thick.
Use a pizza cutter or large chefs knife to cut out 1 1/2 inch squares, in a grid pattern.
Drop 3-4 squares of dough into the hot oil at a time and cook for about 2-3 minutes turning halfway through.
Drain the beignets on some paper towel.
Dust with lots of powdered sugar and serve warm and fresh.