INGREDIENTS

1. Red onions, small to medium size. You will need as many as you can fit in your pan + 2 more.
2. Butter (generous knob)
3. Vegetable oil about 1-2 tbsp
4. Balsamic vinegar about 3-4 tbsp
5. (Golden) sugar about 3 tbsp
6. Thyme, a sprinkle
7. Water about 3 tbsp
8. Puff pastry, 1 pre-rolled sheet or 2/3 of a block

METHOD

1. Melt the butter and oil in a low, oven proof, casserole or oven proof frying pan on a medium heat. Anything with a heavy bottom, flat top and suitable for hob & oven is good.
2. Peel and cut the onions in half crosswise, ie the rings will be showing. Add to pan with cut side down, make sure you cover the whole bottom pan.
3. Pan fry gently until slightly browned, for about 15 min. The onions will shrink slightly, so this is the time to add the extra onions!
4. Sprinkle sugar & thyme over the onions, add the balsamic vinegar and water. Cover with some foil or lid and reduce heat to fairly low. Let simmer for another 20 minutes.
5. Remove foil/lid and turn up the heat slightly to reduce the liquid until it's almost gone and sticky but take care you don't burn the onions. Meanwhile also preheat the oven to 200 degrees 
6. If you use a block puff pastry, roll out to a circle that is a bit larger than the pan you use. If you use a ready sheet, just cut out to size. Larger is better than too small.
7. Turn off heat and place pastry on top off the onions, tuck the pastry nicely in between the onions and around the sides.
8. Place in the preheated oven and bake for 25-30 minutes until pastry is crisp and golden

TO SERVE

1. Remove pan from oven and rest for 10 minutes
2. Place a completely flat and sturdy plate/board on top of the pan, take a deep breath and flip the pan over whilst holding the plate firmly against the pan.
3. Don't worry if any onions have stuck to the pan, you can just place these on the pastry tart.
4. Optionally sprinkle some fresh thyme, feta or goat's cheese over the tart tatin and serve whilst still lukewarm