Preheat your oven to 375℉.
Line a single cup of a jumbo muffin pan with a parchment square or a cupcake liner.
In a small bowl whisk together the all-purpose flour, cocoa, baking powder and salt.
Add the chocolate chips to the dry ingredients and toss to coat. Set aside.
In a separate bowl whisk together the melted butter, sugar, egg yolk, vanilla and yogurt until completed mixed and smooth.
Add the dry ingredients to the wet and using a rubber spatula fold in until just combined. Do not over mix.
Place the batter into the prepared muffin cup.
Bake for about 25 minutes or until the top springs back when lightly pressed. For 2 standard muffins, bake about 20 minutes.
Allow to cool in the muffin pan for 10 minutes. Remove the muffin and place on a wire rack to cool completely.