Homemade Hostess Cupcake Cake

1. Preheat oven to 350° F. Line a 9x13 inch cake pan with parchment paper.2. In a large bowl, beat together the melted butter, eggs, milk, yogurt, sugar, and vanilla. Add the flour, cocoa powder, baking powder, baking soda, and salt. Mix until combined, then slowly beat in the hot coffee until combined.3. Pour the batter into the prepared cake pan. If desired, top with chocolate chips. Bake for 25-30 minutes until the top is just set. Remove and let cool.4. To make the filling. Add the butter, brown sugar, and 1/4 cup water to a pot set over medium heat. Bring to a boil and cook, stirring constantly, until the sugar has melted and the mixture is dark and bubbling, about 5 minutes. Stir in the salt. Turn the heat to low. Add the mini marshmallows and stir until melted, about 5 minutes. Remove from the heat and immediately pour the filling over the cake, spreading quickly with a rubber spatula, leaving a 1/4 inch border around the edge. Chill in the freezer, 30 minutes. 5. To make the glaze. Melt the chocolate and milk together over low heat, stirring often until smooth. Gently pour the glaze evenly over the cake, spreading it just to the border. The more you spread the glaze, the more it will blend into the filling, so work quickly and resist spreading too much. It will not be perfect. Let the glaze set for at least 2 hours or overnight.6. Spoon the melted white chocolate into a piping bag fit with a small round tip. You can also use a sandwich bag and cut the tip of one of the corners off. Draw loops on the top of the cake. Slice and enjoy! It is helpful to clean the knife after each slice. The cake will be a little messy due to the stickiness from the marshmallows! Let go of perfection here!