This is wickedly good: an airy chocolate cake atop a hidden lake of not-too-sweet chocolate sauce spiked with espresso. Make sure you have a bowl of cold, lightly whipped cream to serve with this, or a stash of vanilla ice cream. — Faith Mason, author of Sheet Pan Magic
Place the butter in a 8 x 12 x 2-in sheet pan. Preheat the oven to 325ºF and while it reaches temperature place the pan inside for the butter to melt.
Meanwhile, whisk together the flour, baking powder, sugar and cocoa together in a mixing bowl.
When the butter has melted, pour into a jug and set aside to cool for a few minutes. Meanwhile, brush the pan with the residual butter so all the sides are coated.
Add the milk and eggs to the melted and cooled butter and mix well. Stir this into the dry ingredients to make a smooth batter. Scrape into the buttered sheet pan and smooth the top with a spatula.
Mix all the topping ingredients together with 2 cups just-boiled water and pour over the batter. Bake for about 30 minutes until the top is firm: there will be a pool of sauce under the cake. Serve hot topped with whipped cream or ice cream.
Recipes excerpted with permission from Sheet Pan Magic by Sue Quinn, (Quadrille, October 2017)