Preheat oven to 350 degrees.
In a large bowl, mix together butter, milk, and eggs.
In a separate bowl, sift together flour, sugar, baking powder, salt, and chocolate chips.
Slowly pour the flour mixture into the butter mixture and mix until completely combined.
Fold in raspberries very gently (you don't want your batter to turn pink), reserving a few to put on top of your muffins.
Pour batter evenly into lined muffin cups, filling them about 2/3 of the way full. Top with reserved raspberries and crumb topping (optional).
Bake for 15 - 20 minutes, or until a toothpick placed in the center of a muffin comes out clean.