Preheat the oven 180°C/gas mark 4. Grease a 23cm square baking pan with butter and line with baking parchment

In a heatproof bowl suspended over a pan of simmering water, melt the chocolate and butter, then set aside to cool slightly. In a medium bowl, whisk together the sugars and eggs until pale and thick, for around 3–4 minutes

Whisk in the cooled chocolate mixture then fold in the flour, cocoa and baking powder

In a small bowl, combine the Panko breadcrumbs and sea salt

Scrape half of the brownie batter into the prepared pan then sprinkle over one third of the breadcrumb mixture. Scrape over the remaining batter until covered and level with a spatula

Mix the remaining breadcrumbs with the olive oil until well coated, then sprinkle over the top of your brownie batter

Bake for 20–25 minutes, or until the top is set and slightly crackly and a skewer inserted in the middle comes out with some gooey batter still stuck to it

Allow to cool completely in the tin before cutting into squares and serving. These brownies will keep in an airtight container for 3–4 days