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 2 eggs separately, then stir in the beaten egg, 1 cup whole milk, ½ cup granulated sugar, and ¼ cup unsalted butter. Gently fold in the 1 cup raspberries and ½ cup mini chocolate chips.
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 raspberries, with no need to defrost them first.
Grease the muffin tin well. Muffins that stick to the pan are a bummer! Be sure to really grease the muffin tin with oil or non-stick spray so the muffins will release easily. Or, of course, you can use muffin liners.
Coolbriefly: Let the muffins cool 5 minutes in the tin, then turn them out to cool fully.
Make mini muffins. Grease or line a mini muffin tin 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.
Make these vegan. Swap flax eggs or a mashed banana for the eggs, then use non-dairy milk or water, and oil or non-dairy butter.