Potato, leek and mushroom ‘gratin’

Food waste is big news. And so it should be. It’s estimated that 18 million tonnes of food ends up in landfill every year in the UK alone. Globally the figure is a mind-numbingly huge 1.6bn tonnes, almost a third of what’s produced. At a time when food poverty still affects one in nine people, that just seems wrong.

And as the UK government formally declares a climate crisis, food waste comes high on the agenda of things we can do to make a different. Climate scientists state that reducing food waste is the third most impactful thing we can do (eating a plant-based diet is top of the list!). Which is good news. And there are some great initiatives going on that help get unused food to those who need it (like Fareshare) and even apps that enable you to find someone local who wants your unwanted food (like Olio).

I have found my shopping habits have changed since I started eating a whole-food plant-based diet. For a start, as processed foods and ready meals are off the list, most of the products I buy are either dried, tinned or fresh. We get through a lot of fresh produce in a week. When I’m at home in the UK, a weekly organic vegbox provides us with the main key ingredients for the week and our meals are planned around whatever delights are brought to our door. Then I do one or two top ups in the week for more perishable items like salads and fruit. Whilst I don’t have a rigid programme (I’m much more of a spontaneous cook not a planner!) I do try to be mindful about how much I’m buying to make sure things get used.

But no matter how careful I am, there is always a few bits left over that need using up to save them from the bin (or the compost heap in our case). Just because they’ve been left on the shelf doesn’t mean they can’t be transformed into something delicious.

This potato, leek and mushroom gratin is one of the throw together dishes I created to use up a few things on the cusp of being thrown out. If left too long, leeks can get dry and crispy on the outside, so trim it well before using, but use as much as possible. And mushrooms definitely have a limited lifespan, so try to use these before they start smelling too ripe and mouldy – not a good flavour!

Although this recipe is pretty quick to throw together, time maybe short for you in the week. So cook some extra potatoes a few days before hand. It cuts down on the cooking time here. Although, cold potato doesn’t last long in our fridge if there’s hummus in there too – they make a great snack together!

I’ve been making my own sourdough bread (more to come on that soon). It’s lovely for the first few days but does dry out quite quickly, mainly because it has no oils or additives found in most breads to prolong the shelf-life. So there is always an end piece left-over. Whilst it’s too tough to eat, it makes awesome breadcrumbs. I just throw it in the food processor, pulse a few times then transfer to a pot in the freezer (if I’m not going to use them straight away). Simple!

Of course, if you don’t have potato, leek and mushroom, you can use whatever veggies you have in the bottom of your fridge. Include a few dried herbs too if you wish – thyme tastes lovely with this combination. And if you give this a go, do let me know how you get on. I hope you’ll enjoy the taste as well as the sustainable satisfaction of knowing you’ve done a little bit to help look after our wonderful world.

Potato, leek and mushroom gratin

A simple way of using up bits and bobs left in the fridge. This tasty dairy-free plant-based dinner is a great way of reducing food waste too.
Prep Time 5 minutes
Cook Time 20 minutes
Total Time 25 minutes
Course Main Course
Servings 2


  • 2 large potatoes like baking potatoes
  • 1 large leek
  • 100 grams mushroom of choice washed

For the sauce

  • 75 grams cashew nuts soaked in hot water for 10 minutes
  • 125 ml water
  • 1 teaspoon dijon mustard
  • 1 small clove garlic crushed
  • salt and pepper to taste

For the topping

  • 4 tablespoons breadcrumbs of choice (wholewheat, gluten-free, panko, sourdough)
  • 2 tablespoons nutritional yeast
  • 1/4 teaspoon salt


  • First, scrub the potatoes and cut into thin wedges. Place in a pan, cover with water and bring to the boil. Simmer for 5-7 minutes until cooked but not falling apart. Drain and put to one side.
  • Whilst the potatoes are cooking, wash and trim the leek, keeping as much of the green stem as possible (but discard any woody bits). Slice in half lengthways then cut into rounds. Slice the mushrooms.
  • Heat 2 tablespoons of water in the bottom of a medium-sized frying pan. Add the leeks and a pinch of salt and sauté on a medium heat for 5 minutes until it starts to soften. Add the cooked potato and sliced mushrooms, cover with a lid and sauté on a low heat for another 5 minutes.
  • Whilst the veggies are cooking, make the sauce by placing the cashew nuts, water, mustard, garlic and salt and pepper into the jug of a blend and blitzing to smooth. 
  • Mix the topping ingredients together in a bowl. Pre-heat the grill to high.
  • Pour the sauce into the pan and stir to make sure everything is covered. Heat through for a few minutes without letting the sauce stick to the bottom of the pan. Turn off the heat and sprinkle the breadcrumb mix over the top.
  • Place the pan under the grill, making sure the handle is out of the way. Grill for 4 minutes or so until the breadcrumbs are lightly browned and crispy. Carefully remove the pan and serve.
Keyword dairy free, dinner, food waste, leftovers, plant based, sauce


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