1. Preheat the oven to 200°C, gas mark 6. Line a 20cm brownie tin with baking parchment.
2. In a pan, combine the cream, vanilla, butter and salt over a low heat until just bubbling. Set aside.
3. In another pan, place the sugar and syrup over a medium heat and swirl until the sugar dissolves. Raise the heat and swirl until a golden caramel is reached.
4. Pour over the cream mixture – it will bubble and spit so be careful. Stir until smooth and set aside to cool.
5. For the brownies, melt the butter and chocolate in a bowl over a pan of simmering water. Once smooth, stir in the remaining ingredients until combined, then pour into the tin.
6. Drizzle over 4 tbsp of the cooled caramel then bake for 25 minutes until risen but still with a wobble.
7. Remove from the oven and cool for 1 hour before cutting into 12 squares. Drizzle with caramel and serve with Heston from Waitrose Salted Caramel Popcorn Ice Cream.