Chop the broccoli into small florets and dice the stems then drop into a large pan of (salted) boiling salted and cook for 3 minutes
Drain & refresh under cold water
Wilt the spinach (I cooked mine in a covered bowl in the microwave for 1.5 minutes). Drain and squeeze out the liquid, then chop finely
Mix the defrosted peas, spinach and broccoli together and set aside
Cube the butter and put into a medium saucepan with the milk and flour
Place the pan over a medium heat and cook, stirring constantly with a wooden spoon, until the sauce is smooth and thick (beat with a balloon whisk if the flour needs breaking down)
Take off the heat and add the cheeses, mustard and seasoning (to taste). Stir until the cheese is completely melted and thoroughly combined
Add the prepared vegetables and toss to coat them in the sauce, then divide the mixture between 4 pie dishes
Preheat oven to 180C/ 350F/ GM 4
Peel & chop the potatoes and cook in boiling water until tender, then mash
Stir in the cheeses, followed by the creme fraiche, mustard and some seasoning to taste
Share the mashed potato between the pies and spread out to cover the filling (I piped mine for a neat look, but it's fine to use a fork to spread it out)
Scatter the breadcrumbs over the potato, put the pies onto a baking sheet (to catch any overflowing sauce) and bake for 30-40 minutes until the topping is golden
Serve with a simple green salad
If using fresh peas cook them with the broccoli.
Don't forget, you can bake your potatoes, slit them open, scoop out the flesh and proceed to mash them instead of boiling peeled potatoes in a pan.
This recipe can be made in advance. Once the pies are assembled, let cool to room temperature, then cover and refrigerate until ready to cook. They will need 40-45 minutes from chilled.