Preheat oven to 350º F. Grease or paper-line 12 standard-sized muffin cups.
Add flour, baking soda, salt, cocoa powder, and cardamom to a large bowl and whisk until combined.
In a separate bowl, whisk together egg, brown sugar, vanilla, melted butter, and buttermilk.
Add the wet ingredients to the dry and whisk until just combined, no more than 15 to 20 strokes. Fold in raspberries and chocolate chips.
Spoon a generous ¼ cup batter into each muffin well. Bake for 13-16 minutes, or until muffins are set and a toothpick inserted in the center comes out mostly clean.
Let cool in pan for about 5 minutes before removing to a rack. Serve warm or at room temperature.