Preheat the oven to 400°F. Lightly grease (or line with cupcake papers) a 12-cup square or standard muffin pan, or lightly grease a silicone muffin pan., To make the topping: Mix the ingredients together until the mixture is very moist and crumbly. Set aside., In a large bowl, whisk together the melted butter, milk, and eggs., In a separate bowl, whisk together the flour, sugar, baking powder, salt, and chocolate chips., Add the dry mixture to the liquids and stir until combined., Divide the batter evenly among the muffin cups., Push three small or two large raspberries down into the top of each muffin. They don't need to be covered by batter., Sprinkle the muffins with the crumb topping, using a slightly heaped tablespoon for each one., Bake the muffins for 20 to 25 minutes, until they're golden brown and feel set when you touch them in the middle., Remove the muffins from the oven, and let them stand for 5 minutes before removing from the pan., Store the muffins in an airtight container for up to 5 days, or freeze them for up to a month.