Preheat the oven to 350℉ and line a 12-count muffin tin with cupcake liners.

In a large bowl, whisk together the flour, baking soda, salt, cocoa powder and sugar. Make 3 wells in the dry ingredients: 1 small, 1 medium, and 1 large. Measure the vanilla into the small well, the vinegar into the medium, and the oil into the large. Pour the cold water over top and whisk until the batter is smooth.

Add the softened cream cheese and egg yolk to a small bowl and whip using a handheld electric mixer on medium speed until smooth and creamy. Fold in the chocolate mint pieces.

Fill each cupcake liner half full with the chocolate batter, then drop 1-2 teaspoons of cheesecake filling in the middle of each, finally cover with about 1 tablespoon of the remaining chocolate batter. They should be filled all the way to the top with batter and cheesecake filling.

Bake the cupcakes in the preheated oven for 30-35 minute or until a toothpick inserted into the cake part around the edges of the cupcake comes out clean. Let cool for 10 minutes and then remove from the muffin tin to finish cooling on a wire rack.

Refrigerate until ready to serve. These are great served with whipped cream on top. Enjoy!