Preheat oven to 375 degrees F
Grease jumbo muffin tin (6)
In a large bowl, mix first 5 ingredients (through salt). Make a well in center of flour mixture.
In a medium bowl, combine egg, milk, butter, and vanilla. Add milk mixture all at once to flour mixture and stir just until moistened.
In another bowl, stir together pumpkin and pumpkin pie spice. Spoon half of the batter into pumpkin mixture and stir until combined.
In a small bowl, melt chocolate and mix with yogurt and cocoa powder until smooth. Add to remaining plain batter; stir until combined.
Use medium scoop to scoop chocolate batter and pumpkin batter side by side in muffin tin. Use smalls scoop to continue to fill tins until full. Use toothpick to swirl batters together.
Bake 30 minutes. Cool in muffin tins for 5-10 minutes. Remove from tins and place on cooling rack.
