Generously butter a muffin tin. Preheat the oven to 375℉.
In a large bowl, whisk together the 2 cups whole wheat flour, 3 teaspoons baking powder, 1 teaspoon ground cinnamon, and ½ teaspoon fine sea salt. Lightly whisk the 1 large egg separately, then stir in the beaten egg, 1 cup plain yogurt, ½ cup maple syrup, and ¼ cup oil. Gently fold in the 1 ½ cups blueberries. Batter may not be smooth - that's OK.
Spoon the batter evenly into the muffin tin (fill each cup about two-thirds full). and let the batter rest for up to 20 minutes. Bake the muffins for 15-20 minutes, until a tester comes out clean.
Place the muffin tin on a wire rack to cool for about 10 minutes, then gently turn out the muffins onto the rack to cool completely.
Notes
Use fresh or frozen berries. As noted above, you can use either fresh or frozen blueberries (or try frozen wild blueberries). No need to defrost the blueberries first.
Grease the muffin tin well. Muffins that stick to the pan make me so sad! Be sure to really grease the muffin tin with oil or non-stick spray so that the muffins release easily. Or, use muffin liners.
How to cool: Let the muffins cool 5 minutes in the tin, then turn them out to cool fully.
Make mini muffins. Grease a mini muffin tin (a la my gluten free mini blueberry muffins) and portion out the batter. You will need to bake the muffins a few minutes less if using a smaller size.
Sprinkle on some sugar. For a little extra sweetness, sprinkle granulated or brown sugar over the tops of the muffins before baking.