1. Preheat your oven to 350°F (175°C) and line a muffin tin with cupcake liners.
2. In a medium bowl, whisk together the flour, sugar, cocoa powder, baking soda, and salt.
3. In a separate large bowl, combine the vegetable oil, egg, and vanilla extract, then add the dry ingredients to the wet mixture, alternating with the buttermilk, beginning and ending with the dry ingredients.
4. Fill each cupcake liner about halfway with the batter. Place a piece of dark chocolate and a few raspberries in the center of each, then cover with more batter until the liners are three-quarters full.
5. Bake for 18-20 minutes, or until the tops of the cupcakes are set and a toothpick inserted into the edge (avoiding the molten center) comes out clean.
6. Let the cupcakes cool in the pan for about 5 minutes before transferring them to a wire rack to cool completely.

From my experience, the key to perfect molten centers is ensuring the chocolate is well-covered by batter. This technique was honed over years of making family favorites, where precision was learned through joyful, messy trial and error.