Preheat your oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners.

In a large mixing bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt until well combined.

In another bowl, using an electric mixer, beat the butter and sugar together on medium speed until light and fluffy, about 3 minutes.

Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.

Gradually add the dry ingredients to the butter mixture, alternating with the buttermilk. Mix until just combined, being careful not to overmix.

In a small saucepan, combine raspberries, sugar, cornstarch, and water. Cook over medium heat, stirring constantly, until the mixture thickens. Set aside to cool.

Fill each cupcake liner halfway with batter. Add a teaspoon of raspberry filling to each, then top with more batter, filling each liner about 3/4 full.

Bake in the preheated oven for 18-22 minutes or until a toothpick inserted in the center comes out clean. Allow to cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.

In a large bowl, beat together cream cheese and butter until smooth. Gradually add powdered sugar, then stir in vanilla and mashed raspberries until the frosting is smooth and creamy.

Once the cupcakes are completely cooled, pipe or spread raspberry frosting on top. Garnish each with a fresh raspberry if desired.

Serve the cupcakes freshly decorated at room temperature for the best flavor. These cupcakes make a delightful treat for any special occasion.

Store any leftover cupcakes in an airtight container in the refrigerator for up to 5 days. Bring to room temperature before serving.