Red onion tarte tatin

1. Heat oil and 25 g butter in a frying pan and add onions. Cook over medium heat for about 20 minutes, stirring regularly. The onions should be soft and tinged with colour. Season and add rosemary. Turn into a greased 20-25 cm pan or 24 cm pie dish. Scatter with 50 g cheese. Set aside.
2. Put flour, baking powder and salt in a bowl with remaining cheese. Add 40 g melted butter, the mustard and the egg to the milk and mix well. Pour onto flour. Mix dough with a fork, wooden spoon or hands. It should be quite sticky. Tip out onto a floured surface and press into a circle the size of the pie dish. Transfer to dish and press to seal edges.
3. Bake in a preheated 200 ºC oven for 15 minutes, then reduce oven temperature to 180 ºC for further 10 minutes. The dough should be golden and crisp. Allow to stand for a couple of minutes. Cover with a large plate and turn upside down. Put on a flat surface and reverse the dish. Scatter with hazelnuts and serve with chutney.