Preheat oven to 350 degrees. Butter and flour a baking dish, I used a 9x9 square pan, but feel free to use whatever you have available. These would also be fantastic muffins, just reduce the cooking time by half.
In a large bowl using a hand mixer, beat butter and sugar until light and fluffy. Add in eggs, one at a time, mixing well after each addition. Add in pumpkin, sour cream, bourbon, and vanilla extract and blend well.
In a medium bowl combine flour, baking soda, cinnamon, cardamom, and salt. Gradually beat the flour mixture into the pumpkin mixture.
Scrape batter into baking dish and top with streusel. Bake for 40 minutes, or until a knife/toothpick inserted comes out clean.
Cool for at least an hour, slice into 9 servings, and enjoy!