Whisk together dry ingredients.
Add butter and mix on low until butter is in blueberry sized chunks, about 2 minutes.
Add sour cream and mix until shaggy, about 1 minute.
Turn out on floured surface, adding flour if wet.
Fold until no dry patches remain.
Gather and refrigerate for at least 30 minutes.
Tri-fold three times to laminate.
Wrap and refrigerate for 30 minutes.
Roll to about ⅛ inch.