• Preheat your oven to 350° F and spray a 9x13” pan with baking spray.
• In the bowl of a stand mixer fitted with the paddle attachment, add the 1 1/2 cups sugar, 1 1/2 cups flour, 3/4 cups cocoa powder, 1/2 tablespoon baking soda, 3/4 tsp baking powder, and 1/4 tsp kosher salt, and mix on low until combined.
• Add the 2 eggs, ½ cup yogurt or sour cream, and 2 tsp vanilla extract. Mix until combined. The mixture will be crumbly.
• With the mixer running on low speed add in the ¾ cup boiling water and 1/4 cup oil slowly.
• Continue mixing until the batter is evenly mixed.
• 
  Pour into the prepared pan and bake for 20-25 minutes.
• 
  Cool the cake in the pan for 20 minutes then add the whole package of marshmallows on top. Feel free to use more if you want!
• 
  You can either torch the marshmallows with a kitchen torch (my preferred method) or return to the oven for 5 minutes to brown.

Make the frosting

• In a medium microwave safe bowl melt the ½ cup butter for 30 seconds at a time until melted.
• Add the ⅔ cocoa powder and mix well until smooth. There should be no lumps from the cocoa powder.
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  Sift the powdered sugar on top, and add the ½ cup cream. Whisk until smooth, then slather on top of the marshmallows and enjoy!