01 -
1 sheet thawed puff pastry.
02 -
1 yellow onion, cut into thin rings.
03 -
3 tablespoons honey, divided.
04 -
2 sprigs fresh thyme.
05 -
Sea salt to taste.
06 -
Black pepper to taste.
07 -
18 thin slices gruyere cheese.
08 -
1 large egg for washing.