In a large bowl whisk together the sour cream, sugar, buttermilk, butter, and egg until smooth.

Add the baking powder, baking soda, salt, and vanilla, whisk to combine.

Add the flour and stir it in until just combined, with no dry patches. Cover with plastic wrap and place it in the refrigerator for at least 5 hours, up to overnight.

Preheat the oven to 350°F. Line sheet trays with parchment paper, set aside.

Generously flour a clean work surface. Take 1 ½ tablespoons worth of dough (I used a cookie scoop), place on the work surface, coat the outside of the dough with flour, move to a lightly floured surface, roll it out into an 8-inch long rope.

Pinch the ends together to form a circle, flip the dough over to form a figure 8, place it on the sheet tray.

Repeat with the remaining dough, placing the cookies about 2 inches apart.

Bake for 7-8 minutes until puffed and the outside of the cookie appears dry. The bottoms will be lightly golden brown. Let cool on the sheet tray for 2 minutes, transfer to a wire rack to cool completely.