Rocky Road Pancakes

Combine milk and vinegar in a large bowl. Set aside for 5 minutes.

Meanwhile, combine flour, sugar, cocoa powder, baking powder, baking soda, and salt in a medium bowl.

Whisk eggs, butter, and vanilla extract into the milk-vinegar mixture. Add flour mixture and whisk until no lumps remain. Gently fold in marshmallows and walnuts.

Heat a lightly oiled griddle over medium-high heat. Drop 1/3 cup of batter onto the griddle for each pancake; cook until tops begin to bubble, 3 to 4 minutes. Flip and cook until browned on the other side, 2 to 3 minutes. Repeat with remaining batter.