150 g (5 oz) unsalted butter, plus extra for greasing
150 g (5 oz) plain dark chocolate, broken into small pieces
100 g (3 1/2 oz) dulce de leche or thick caramel sauce
2 large eggs
75 g (3 oz) soft dark brown sugar
75 g (3 oz) caster sugar
1/4 teaspoon salt
50 g (2 oz) self-raising flour
100 g (3 1/2 oz) walnut pieces, chopped
1 teaspoon sea salt flakes
Grease a 30 x 20 cm (12 x 8 inch) brownie tin and line with nonstick baking paper (see page 9). Place the butter and chocolate in a small saucepan over a low heat and warm until just melted. In a separate saucepan, gently warm through the dulce de leche or caramel sauce.
Meanwhile, place the eggs, brown sugar, caster sugar and salt in a large bowl and whisk until combined. Using a rubber spatula, stir in the melted chocolate, flour and half of the chopped walnut pieces.
Scrape the mixture into the prepared tin. Scatter over the remaining walnuts, then drizzle with the dulce de leche or caramel sauce and sprinkle with the sea salt flakes.
Bake in a preheated oven, 200°C (400°F), Gas Mark 6, for 15–18 minutes until just firm to the touch, but with a slightly fudgy texture.
Leave to cool in the tin for 1–2 minutes, then lift on to a board using the lining paper and cut into 12–16 squares. Serve warm or cold.