Poach or cook the fish in the microwave with butter and white wine. Do not over cook the fish as it is going to be cooked again in the pie, it should have an opaque appearance and flake easily. Allow fish to cool in stock.
When fish is cooled, drain off and keep the 'stock', remove any skin and flake fish into large pieces, divide between the dishes along with the broccoli florets.
In a food processor or liquidiser, blitz the watercress with the crème frâiche or cream, add the fish stock and then pour over the fish filling in the dishes.
Cut 6 lids from each pastry sheet, use pastry trimmings to make a rim around top edges of dishes. Place lids on top, press well down around edges and make a small hole in top of each. Brush tops with beaten egg and if desired sprinkle with sesame seeds.
Bake in preheated oven for approx. 20 minutes until pastry is golden brown.