Scrape the mixture down, and stir a little with a spatula, then pour this dark, liquid batter into the prepared tin. If it looks too dry – it should be quite runny – add a little water plus a splash more olive oil. Bake for 35 minutes or until the sides are set and the very center, on top, still looks slightly damp. A cake tester should come up mainly clean but with a few sticky chocolate crumbs clinging to it.