A great decadent side to your Christmas Roast, this Potato Gratin with Porcini Mushrooms is decadent and filling enough to stand as a main dish on its own. Creamy, with strong earthy aromas of porcini and thyme, our Potato Gratin goes very well with beef, lamb or gammon, or simply with a variety of steamed vegetable sides!
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If you are a lover of mushrooms, and specifically the deep earthy favours of porcini, this gratin is no less than heavenly! We are very lucky, we often get wild dried porcini from my aunt whose husband goes foraging every autumn for them, but when we run out, we buy the Sous Chef Wild Porcini Mushrooms. They are delicious and normally quite small, so they rehydrate quicker.

What Potatoes to Use?
To make this gratin, you will ideally need floury potatoes. They cook quicker and the texture is more suited for most of the gratins and oven cooked potato dishes. We like using King Edward or Maris Piper potatoes for this. They soak up the sauce well and take in all the flavour of the porcini.

How to Make Potato Gratin with Porcini Mushrooms?
Chop the shallots and garlic finely. Pour the milk and double cream into a large pan. Add dried porcini mushrooms, thyme, garlic, shallot, nutmeg and a tsp of salt. Bring the mixture to a gentle boil and simmer for 5 minutes. Then cover with a lid and leave to cool down for 30 minutes.
Pour the cooled mixture into a blender/ smoothie maker/liquidiser and blitz into a smooth liquid.
Peel the potatoes and using a mandolin or a food processor with a slicer attachment, slice the potatoes into 2-3mm thick slices.
Preheat the oven to 150°C Fan. Grease an ovenproof dish with butter generously.
Layer a quarter of the potatoes to cover the bottom in an even layer. Pour a quarter of the cream mixture. Then layer another quarter of the potatoes and top with the sauce again. Carry on like this until you have no potatoes or sauce left.
Top the gratin with grated parmesan, a sprinkling of salt and pepper. Cover the dish with foil and pop into the oven for 1-1.5 hours. After an hour, uncover the dish and check if potatoes are cooked through and tender by inserting a sharp knife. Once cooked, increase the oven temperature to 180°C and place the uncovered dish back in the oven for another 10-15minutes.
If you’re looking for ideas for sides for your festive meal, have a look at our other recipes below:

Potato Gratin with Porcini Mushrooms
Equipment
- Mandolin or Food Processor with Slicer Attachment
- Blender/ Smoothie Maker
Ingredients
- 800 g King Edward or Maris Piper Potatoes
- 400 ml double cream
- 150 ml milk
- 15 g dried porcini mushrooms
- 1/2 tsp fresh thyme chopped
- 1 shallots roughly chopped
- 2 garlic cloves roughly chopped
- 1/4 tsp nutmeg
- 15 g butter
- 30 g parmesan
Instructions
- Pour the milk and double cream into a large pan. Add dried porcini mushrooms, thyme, garlic, shallot, nutmeg and a tsp of salt. Bring the mixture to a gentle boil and simmer for 5 minutes. Then cover with a lid and leave to cool down for 30 minutes.
- Pour the cooled mixture into a blender/ smoothie maker/liquidiser and blitz into a smooth liquid.
- Peel the potatoes and using a mandolin or a food processor with a slicer sttachment, slice the potatoes into 2-3mm thick slices.
- Preheat the oven to 140°C Fan. Grease an ovenproof dish with butter generously.
- Layer a quarter of the potatoes to cover the bottom in an even layer. Pour a quarter of the cream mixture. Then layer another quarter of the potatoes and top with the sauce again. Carry on like this until you have no potatoes or sauce left.
- Top the gratin with grated parmesan, a sprinkling of salt and pepper. Cover the dish with foil and pop into the oven for 1-1.5 hours. After an hour, uncover the dish and check if potatoes are cooked through and tender by inserting a sharp knife. Once cooked, increase the oven temperature to 180°C and place the uncovered dish back in the oven for another 10-15minutes.
Nutrition

Such a perfect side dish for special occasions!! Thank you so much for sharing this recipe!
You are most welcome, Toni!
This potato gratin was so rich and delicious! I love the flavour that the mushrooms added.
Didn’t think you could make potato gratin any better but adding mushrooms! What a game changer! Thanks for the delicious recipe.
Thanks! Glad you liked it 🙂
This was a such a delicious and easy recipe! It went perfect with my dinner meal. So good!