For the pastry, add salt, thyme, and butter to the flour. Add 1 beaten egg and knead the pastry lightly using ice-cold water. After kneading, wrap the pastry with cling film and keep it in the refrigerator for at least 20 minutes.
Roll a piece of dough from the pastry into a flat disk. Spray the 24 cm tart tin with cooking spray and line the pastry inside it. Press the pastry inside the tin and let the excess of the dough overhang.
Lightly prick the base of the pastry with the fork and chill it in a freezer for around 30 minutes. Cut the baking paper into a circle larger than the tart. Press it against the inside of the tart case. Fill baking beans in the tart case and bake them for about 20 minutes.
Remove the beans and baking sheet. Brush the case with yolk and bake again for 5 minutes. Brush it again with yolk and bake it for 10-15 minutes until it turns golden brown.
For the custard, beat the eggs, milk, creme fraiche, yolk, tarragon, a pinch of salt, and pepper.
To make the filling, saute the bacon pieces in a pan containing olive oil for about 5 minutes until they’re crispy and brown. Now, add onion, chicory, to the pan containing bacon and oil. Cook for 5 minutes, stirring continuously. Strain the juice using a sieve and transfer them to a big bowl.