Preheat oven to 350F while you prep the batter.
Sift and whisk dry ingredients in a large bowl until combined.
Add wet ingredients and mix with a spatula until smooth. Add blueberries and walnuts and stir to combine.
Spoon batter into muffin liner cups, leaving about a centimeter of space at the top of the cup.
Bake for about 20-25 minutes or until tops are golden brown. You can check to see whether the muffins are finished by poking a toothpick into the center of the muffin. When the toothpick comes out clean, they're ready!
Allow for muffins to cool completely before freezing (if saving leftovers).