Preheat oven to 350. Grease and flour or line 12 wells in a muffin tin. Set aside.
In a large bowl or blow of a stand mixer, whisk together the flour, sugar, baking powder, and salt.
Beat in the ricotta, oil, milk, egg, and vanilla until smooth.
Fold in the blueberries and walnuts. Evenly divide the batter into the 12 wells of the muffin tin.
Bake for 20 minutes or until a toothpick inserted in the center of the center muffin comes out clean.
Cool in pan on a wire rack for 10 minutes. Invert the muffins and serve or continue to cool.