250g (9oz) butter
375g dark chocolate, broken into pieces
70ml (2.5fl oz) water
1g (1⁄4 teaspoon) cannabis flower
6 medium eggs
450g (16oz) caster (superfine) sugar
200g (7oz) plain flour
20g (3⁄4oz) cocoa powder
1/2 teaspoon salt
100g (31⁄2oz) nuts (optional)
METHOD
Preheat the oven to 120°C fan/250°F/gas 1⁄2 and line your 22 x 33 x 5cm (81⁄2 x 13 x 2in) baking tray (sheet pan).

To make the cannabis butter, begin by breaking up your green herb into smaller florets and running a knife through them on a chopping board.
Then place on a tray lined with greaseproof paper, cover with another layer of paper, then place a second tray on top. This will stop any weed dust blowing around and getting up in your grill, but also stop things from burning. Place in the oven for 30 mins. This stage is called decarboxylation (or decarbing) and it is very important. Once you have taken the weed out of the oven turn it up to 160°C fan/320°F/gas 4.
Now infuse your butter by placing it in a heavy based pan with the water and the weed, and gently heat to melt the ingredients together. The water will stop things from burning, so don’t worry if the pan starts to simmer.
Leave on a very low heat for at least 30 minutes or until most of the water has evaporated, leave to cool for 15 minutes or so to allow it to continue infusing. Strain the butter through a fine sieve to remove the green flecks of herb.
Pop the infused butter back in the pan, add the chocolate and melt together on a low heat.
In a mixing bowl, beat the eggs on a high speed until they begin to foam and add the sugar a little bit at a time until you have a foamy custard. Keep the mixer turning at a high speed, and slowly pour in the melted butter and chocolate.
Sift the flour, cocoa powder and salt into the mixing bowl and lightly combine. Scrape down the sides and bottom of the bowl, then add the nuts (if using). Give a final gentle mix and then pour the mixture into a lined tray and bake for 30 to 35 minutes at 160°C fan/320°F/gas 4.