Preheat the oven to 200 ° C (390 °F).
Heat butter in a large pan.
Add in onions and saute until brown (5 min.).
Stir in mushrooms, adjust salt and pepper and cook until mushrooms release their juice (add a dash of water if needed).
Keep on simmering until the juice has completely evaporated.
Pour in wine and marsala and keep on simmering until evaporated.
Stir in sour cream and herbs and mix until combined.
Line a pie tin with the diameter of 20 cm (8'') with baking paper.
Cover the bottom and sides with a sheet of puff pastry, remove excess pastry.
Stir in filling and spread evenly.
Top with the second sheet of puff pastry, seal edges and remove excess pastry.
Brush with maple syrup and top with sesame seeds.
Bake for 40 minutes in the center of the oven.