Preheat oven to 425°F (220°C). Line a muffin tin with paper liners.

In a large bowl, whisk together flour, granulated sugar, brown sugar, cocoa powder, baking powder, baking soda, and salt. Set aside.

In a separate bowl, whisk together granulated sugar, brown sugar, and eggs until combined.

In a separate bowl, whisk together granulated sugar, brown sugar, and eggs until combined. Stir in Greek yogurt, vegetable oil, melted butter, buttermilk, and vanilla extract to the egg mixture.

Gradually add the wet ingredients to the dry ingredients, mixing until just combined. Be careful not to overmix.

Gently fold in the semisweet chocolate chunks.

Fill muffin liners evenly with batter. Press additional chocolate chunks into the top of each muffin. Bake for 5 minutes at 425°F, then immediately reduce temperature to 350°F (175°C) and bake for an additional 15-20 minutes, or until a toothpick inserted into the center comes out clean.

Let muffins cool in the tin for a few minutes.

In a heat-safe bowl, combine chocolate chips and heavy cream. Microwave in 20-second intervals, stirring after each, until chocolate is melted and smooth. Let cool slightly.

Use a small spoon to create a well in the center of each slightly cooled muffin.

Fill the well with a spoonful of the cooled ganache.

Let muffins cool completely before serving.