In a medium-sized mixing bowl, cream together the butter, vegetable oil, and sugars. Add the eggs, beating to combine.
In a separate bowl, whisk together the oat flour, almond flour, baking powder, baking soda, cinnamon, and salt.
Beat the flour mixture into the butter mixture alternately with the milk, beginning and ending with the flour and making sure everything is thoroughly combined. Fold in the blueberries.
Preheat the oven to 425°F. Divide the batter into the 12 muffin cups, filling up each one almost to the top. Rest the batter while the oven heats.
Bake the muffins for about 18-20 minutes, until golden brown and a cake tester inserted into the middle of one of the center muffins comes out clean.
Remove the muffins from the oven, and let them cool for a couple of minutes in the pan, then turn them on onto a rack to cool completely.
Serve the muffins warm or at room temperature.
Notes
Rest the batter – Like all gluten-free flours, oat flour benefits from a rest before baking off the batter. You can set a timer for 20 minutes, or let the batter rest while the oven preheats to help it hydrate.
Fill the muffin cups ⅔ full for this recipe – While some muffin recipes advise filling the muffin cups to the brim, I’ve found that about ⅔ full is the sweet spot so that they rise nicely but don’t overflow.
Go dairy-free - Instead of butter, use melted coconut oil or melted non-dairy butter plus your favorite non-dairy milk.
Refined sugar-free - Add honey or maple syrup to the batter instead of the sugar - a bonus is that you can cut the added sweetened by ¼ cup if you wish.
Add poppy seeds - For a little crunch, stir in 3 tablespoons of poppy seeds to make blueberry poppy seed muffins.
A pinch of cinnamon - I love a little extra warming spice in this recipe. A bit of ground cinnamon or cardamom is perfect.
Storage
Counter – Keep muffins in an airtight container on the counter for up to 3 days.
Fridge – Place muffins in an airtight container for up to 5 days in the refrigerator. You can eat them cold, let them come to room temperature, or gently reheat them in a toaster oven or microwave.
Freezer – Put the muffins in a freezer-safe, sealable bag and store them in the freezer for up to 3 months. Defrost in the fridge before serving.