It is recommended to use fresh raspberries for this recipe. If you have to use frozen raspberries, don't thaw them first and be prepared for the colour to leak quite a bit into the batter.
1. Preheat oven to 375F degrees. Spray muffin pan with non stick spray or line the tins with paper liners.
2. In a large bowl, mix together flour, baking powder, salt, and cinnamon. Mix until all dry ingredients are combined.
3. In a medium bowl, whisk together eggs, granulated sugar, and brown sugar until combined. Mix in milk, oil, and vanilla extract. Mixture will be pale and yellow. Fold wet ingredients into dry ingredients and mix everything together by hand. (don't overmix – that always makes muffins dry) Slowly mix until the flour is off the bottom of the bowl and no big pockets of flour remain. The batter will be thick and lumpy.
4. Stir in the chocolate chips, then delicately fold in the raspberries. The less you mix them, the less the colour will run.
5. Spoon batter into prepared muffin tins, about 3/4 of the way full.
6. Bake at 375F degrees for 18 minutes (or 11-12 minutes if you are making mini muffins). Allow to cool for 10 minutes.