Method

1. Pre heat oven to 180°C/Gas 4.
2. In a large roomy bowl rub the butter into the flour until it resembles
3. breadcrumbs. Stir in the cheese, mustard powder. Add 1-2 dessertspoons of cold water gradually and bring together with your finger tips to make a smooth dough. Wrap in cling film and refrigerate for 30 minutes.
4. Lightly oil the tart tins. Roll out the dough and line the tart tins. Prick with a fork. Bake in the preheated oven for 15-20 minutes until lightly golden. Cool on a wire rack.
5. They can be stored in an airtight container for 1 week. Peel, half and slice the onions very finely. Over a medium heat melt a dessertspoon of butter and sauté the onion for 3 minutes. Add the balsamic vinegar and 6 of the sage leaves finely chopped. Season with salt. Allow to cook slowly until the vinegar has reduced and the onion is soft. Set aside to cool.
6. This can be made a day or two in advance and then the tarts assembled and baked when needed. Before baking, brush the tart cases with beaten egg and bake in a preheated oven for 5 minutes to seal and crisp the pastry.
7. Fill the cases with the red onion mixture. Slice the goat’s cheese log into 6 rounds. Place a round on top of the onion mix.
8. Dip the sage leaves in olive oil and place 1 on each tart. Sprinkle with a little cayenne pepper. Bake for 20 minutes.
9. Serve with a little dressed rocket salad leaves.