Preheat the oven to 180 degrees Celsius.
Place your grapes onto a lined baking tray, and, with a spray of olive oil, into the oven for 20-30 minutes, until they are roasty and have taken on lots of colour.
While the grapes are cooking, place all the ingredients for the tart base into your food processor (if you're making your own hazelnut meal, do so beforehand) and process until a dough ball forms. Remove from the food processor, and press into a fluted tart tin. (between 23-25cm in diameter) Use a fork to poke numerous air holes in the base, and then place the tart in the oven for 10 minutes, to pre cook the base.
Once the base has cooked and cooled, whisk together your eggs, milk, salt, pepper, and sage. Assemble the tart by laying half your cheese (whether you grate the cheese or just spread it in blobs depends largely on which cheese you decide to use - grate the cheddar, blob the blue, etc) on the base. Lay the roasted grapes in the centre of the tart, and pour the whisked egg mixture around them. Finish with the remaining 50g of cheese, and then place the tart into the oven for 30 minutes (checking intermittently - spray the grapes with some olive oil if you're worried about them) or until the egg is fully cooked and the top is beautiful and brown.