Heat the oven to 220°C/200°C fan (425°F), Gas Mark 7.

While the oven is warming, put the nuts on a baking tray lined with baking paper and lightly brown in the oven for six to eight minutes; do watch carefully as they burn easily. Use the paper to shoot the nuts onto a plate to cool. Return the paper to the tin. Turn the oven off and close the door to retain the heat, as you'll use it again later.

Line a 20-centimetre square cake tin or similar-sized ovenproof dish with baking paper. Soak the dates, if using, in the hot water for a couple of minutes. Use a fork to mash them to a purée.

Roughly chop the nuts; each nut should be cut into around four pieces. Reheat the oven to 220°C/200°C fan (425°F), Gas Mark 7.

Place the chocolate and butter in a small heatproof bowl and melt together in the microwave for a couple of minutes. If you don’t have a microwave, melt the chocolate and butter in a glass or metal bowl over a pan of simmering water, ensuring the bowl does not touch the water.

Add the date purée or erythritol and stir through. If your butter does not contain salt, add a pinch now. Add the remaining ingredients, including the chopped roasted nuts, and stir through to combine. Spoon the mixture into the prepared tin and bake for about 15 minutes until firm to the touch. Remove from the oven and leave to cool in the tin for 10 minutes or so.

Use the paper to remove the brownies from the tin, then cut into 18 squares. Serve at room temperature on their own or with Greek yoghurt or whipped cream and a dash of vanilla extract.