Method

1. Preheat oven to 160°C (140°C fan-forced). Grease a 16cm x 26cm shallow slice tin with melted butter and line the base and long sides with one piece of baking paper.
2. Place the chocolate and butter in a medium heatproof bowl over a saucepan of gently simmering water (don't let the base of the bowl touch the water). Stir occasionally until chocolate and butter melt and the mixture is smooth. Remove bowl from saucepan and set aside.
3. Use an electric mixer with a whisk attachment to whisk the eggs and sugar until thick and pale. Add the melted chocolate mixture and vanilla and whisk to combine.
4. Sift together the flour, cocoa powder and baking powder. Add to chocolate mixture and whisk on low speed until just combined. Pour mixture into prepared tin and spread evenly with the back of a spoon.
5. Dot the brownie mixture with spoonfuls of the dulche de leche, dividing evenly. Tap the tin on the benchtop to settle the mixture. Bake in preheated oven for 30-35-minutes or until moist crumbs cling to a skewer inserted in the brownie part. Remove from the oven and cool in tin on a wire rack (this will take about 2 hours).
6. Remove brownie from the tin using the baking paper to lift it out. Cut into portions and sprinkle with cocoa powder or icing sugar to serve, if desired.