Mix flour, sugar, baking powder, baking soda and salt in medium bowl

In a large bowl add buttermilk, butter, eggs, and vanilla and whisk together

Slowly add dry mixture to wet ingredients and stir until no lumps remain

Carefully fold in blueberries, careful not to stir very much if you are using frozen or the color will bleed into your batter

Spray crock very well with nonstick spray

Poor batter into crock and cover

Cook on high for 2 hours until edges are slightly browned and the center is fully cooked through

Let cool uncovered for 10 minutes then slice and serve