01 -
Pop butter and oil in a big pot over medium. Toss in the onions and stir them around till they're coated. After 10 minutes and a sprinkle of salt, give them a stir every handful of minutes. When 30 minutes pass, lower the heat. At the 40-minute mark, add sugar. Keep stirring now and then till the onions turn a rich, golden brown—this takes about an hour.
02 -
Pour in white wine to loosen up those dark bits stuck to the bottom once the onions look jammy. Stir, then move onions off the heat to cool for a little while.
03 -
Switch your oven on to 200°C. Roll out the puff pastry and cut both sheets along the seams so you get 6 pieces. Chop each one into 3 squares so you have 18 in total. Lightly score a border, about 1.3 cm around each square, for the edges to puff up nicely.
04 -
Set out two baking trays lined with parchment. Lay the pastry squares out and keep a couple of fingers’ width between them.
05 -
Use the egg to brush just the edges of your pastry squares. Plop a teaspoon of fig jam right in the middle, then a spoonful of onions, and top with a good pinch of blue cheese.
06 -
Slide those trays in the oven and bake for 18 to 20 minutes. You want those pastries super golden and crispy.
07 -
Pull the tarts out when they're ready. Scatter over some fresh thyme and give each tart a quick honey drizzle. These are awesome warm but honestly, room temp is good too.