01 -
Pour a good splash of olive oil into a big frying pan on medium heat. Toss in the leek rounds with a pinch of salt, cooking for 3-4 minutes each side until they turn golden brown. Scoop them out and put aside.
02 -
Using the same pan, drop in the butter and melt it over medium heat. Toss in the garlic and mustard powder, mix well with a whisk, and let cook for a minute until soft. Sprinkle in the flour, keep whisking for 2-3 minutes to form a thick mix. Slowly pour in milk bit by bit, whisking after each splash until smooth. Let it bubble gently for 8-10 minutes, giving it a stir now and then, until it gets thick and shiny.
03 -
Add the shredded cheddar, cooked leeks, and butter beans into your sauce. Sprinkle with salt and black pepper. Take it off the heat and let it cool down.
04 -
Turn your oven on to 180°C (with fan)/390°F/gas 6.
05 -
On a lightly floured area, roll out 2/3 of your puff pastry until it's 3-4 mm thick. Cut out 6 circles big enough to line six 13 cm pie dishes. Push the pastry into each dish so it comes up a bit over the edges.
06 -
Drop three big spoonfuls of filling into each pastry case, making sure it stays just under the rim. If you've got extra filling, save it for more pies or eat it on the side.
07 -
Roll the leftover pastry to 3-4 mm thickness and cut 6 circles that match your pie dishes. Brush beaten egg around the edges of your pie bases, then lay the pastry circles on top. Pinch the edges together, poke the tops with a knife, and brush them with egg.
08 -
Set your pies on a baking tray and brush with egg again. Pop them in the oven for 35-40 minutes until they're golden and crunchy. Enjoy with mash, gravy, and some greens.