Turn oven to 300°F / 150°C and leave the cake in for another 20 minutes. Check if the middle is solid enough by shaking the cake with the tin gently. If the middle of the cake wobbles it means that there is still fluid inside. If the inside is still wobbly and the outside hasn't turned to coal yet then put the cake back and check it every 10 minutes if it's ready. When the outside of the cake reaches our predefined limits of edibility take it out of the oven anyway and accept defeat. The cake will still be edible but with a runny inside much less presentable so we may have to eat it up the whole alone or feed the kids with it as a healthy breakfast option.