Prepare the Sweet Potatoes: Peel and cube 1 medium sweet potato into bite-sized pieces. Cook in boiling water for about 10 minutes until very tender, then drain and cool.

Mash the Sweet Potatoes: Transfer cooled sweet potatoes to a mixing bowl and mash until smooth and free of lumps.

Mix Dry Ingredients: In a large bowl, sift together 1 cup of flour, 1/3 cup cocoa powder, 1/2 cup sugar, 1 teaspoon baking powder, and 1/2 teaspoon baking soda. Set aside.

Combine Wet Ingredients: In another large bowl, whisk together 1 egg, 1/3 cup vegetable oil, 1/2 cup milk, 1/4 cup yogurt, and the mashed sweet potatoes until well combined.

Combine Wet and Dry Ingredients: Fold the dry mixture into the wet mixture until just combined, avoiding overmixing.

Add Chocolate Chips: Gently fold in 1/2 cup of chocolate chips until evenly distributed throughout the batter.

Prepare for Baking: Preheat oven to 400°F (200°C) and prepare a muffin tin with liners or spray. Fill each muffin cup about two-thirds full with batter.

Bake the Muffins: Bake for 5 minutes at 400°F, then lower temperature to 350°F (175°C) and bake for an additional 20-25 minutes until a toothpick comes out clean.

Cool and Serve: Let muffins cool in the pan for 5 minutes before transferring to a wire rack. Enjoy warm or store for later.