Foryoueats: The World's Best Chocolate Oatmeal Cake

Ingredients

• 1 cup brown sugar
• 1 cup white sugar
• 1/2 cup butter, melted
• 2 eggs, lightly beaten with fork
• 1 3/4 cups flour
• 1 teaspoon baking soda
• 1/2 teaspoon salt
• 1 1/2 tablespoons unsweetened cocoa powder
• 1 cup quick cooking oats*
• 1 3/4 cups boiling water
• 1 12 oz bag chocolate chips, divided (go for the Ghirardelli*)
• 6 tablespoons butter
• 6 tablespoons milk
• 1 1/2 cups sugar
• 1/2–3/4 cup chocolate chips (Ghirardelli again, please)
• 1/2–3/4 cup mini marshmallows*