Preheat oven to 350ºF (175°C). Line muffin tins with baking liners. In a small mixing bowl, beat cream cheese, 1 egg and sugar until light and creamy; set aside. In a large bowl, combine flour, brown sugar, ½ cup (125 ml) granulated sugar, cocoa powder, baking soda, baking powder and salt; mix well. In a separate bowl, beat buttermilk, remaining eggs, oil and vanilla until well combined. Add buttermilk mixture to flour mixture; beat for about 2 minutes, scraping the sides of the bowl as
necessary. Divide batter between muffin tins, filling ¾ full. Spoon a heaping Tbsp of cream cheese mixture over each filled cup; gently swirl with the tip of a knife to get the marbled effect. Bake until cake tester inserted in centers comes out clean, about 20 to 25 minutes. Rotate tins halfway through the baking process, to promote even baking. Remove from oven; cool in pan for 5 minutes. Remove cupcakes from pan and transfer to cooling racks to cool completely. Makes about 20 cupcakes.