Heat a drizzle of oil in a large non-stick pan
Add the onion and fry on a medium heat for 5 minutes until soft
Stir in the butter until melted and sizzling, then add the flour and stir on heat until absorbed and pale and bubbling
Slowly add the milk a little at a time, stirring continuously until it thickens and comes to the boil before adding more
When all milk is used, add the frozen veg, grated cheese, worcestershire sauce and fresh herbs, season with salt and pepper
Roll out one sheet of pastry and cut out 2 circles around 17cm across
Cut out 2 more circles the size of the top of the muffin holes
Grease the muffin tin holes with olive oil using a pastry brush
Push the large pastry circles into the muffin holes, pressing gently and letting pastry overhang by 2-3cm
Repeat with the other pastry sheet, cutting out 2 more big and 2 more small circles
Put the filling in the pastry cases almost to the top
Place the smaller circles on top and gently press the edges into the sides
Fold over the overhanging pastry edges, crimping into a crust
Brush the top and crust with beaten egg
Bake in the oven for 25 minutes
