Serves: 24 brownies1) Position a rack in the middle of the oven and preheat to 180C/Gas 4.
2) Line a 33cm by 23cm by 5cm-brownie pan with parchment or wax paper, so that the edges of the paper come up the sides. Lightly butter the paper.
3) In a medium bowl, whisk together the flour, baking powder and salt. Set aside.
4) Combine the milk and plain chocolates with the butter in a heatproof medium bowl.
5) Fill a medium saucepan with a couple inches of water and bring to a gentle simmer over medium heat. Turn off the heat.
5) Set the bowl on the saucepan, over the heated water, to melt the chocolate gently. Whisk until smooth.
6) In a large mixing bowl, whisk together the sugar, eggs, and vanilla. Stir the chocolate mixture into the egg mixture until evenly combined.
7) Add the dry ingredients and mix just until blended. Take care not to over mix the batter. Transfer the batter to the prepared pan.
8) Bake for about 25 to 30 minutes, until a toothpick inserted into the center of the brownies comes out coated with a fudge-y crumb. Cool the brownies in the pan and on a rack.
9) To make the glaze, put the milk chocolate in a medium heatproof bowl.
10) In a small saucepan, boil the double cream, and pour it over the chocolate. Let stand for 5 minutes, then stir until melted and smooth.
11) Spread the glaze evenly over the brownies and leave to set at room temperature.
12) Lift the edges of the paper to take the brownies out of the pan. Cut into 24 squares. Serve.