A hearty sweet potato mushroom soup, great for the winter months. The sweet potato, mushrooms, and leeks add their own distinctive notes to the underlying beef stock. Though don’t underestimate the contribution of the roasted garlic.
Sweet potatoes are the key to this soup. Regular potatoes would work, but the added depth of flavour that one gets from sweet potatoes elevates this dish from pretty good to exceptional. In addition, sweet potatoes have many health benefits that regular potatoes don’t.
The base stock in any soup is critically important. I strongly encourage you to make your own beef stock. It means a bit more pre-planning and prep work, but the stock will be so much better. To make that extra effort worth it, make way more than you need and freeze it for next time. Whether this beef stock, chicken, salmon head, pork, or veggie stock, you really need some in your freezer.
Roasted garlic is great on its own, with biscotti or baguettes, or for the sweetness and umami character that it adds to this sweet potato mushroom soup. Instructions for preparing it are here.
I have become a fan of using egg yolks as a thickener. Whisk them into a 1/2 cup of cold stock and add that to the soup towards the end of the process. Using egg yolks results in a velvety soup texture, quite different from that resulting from using cornflour.
Sweet potato mushroom soup
- 3 large sweet potatoes
- 3 medium leeks
- 200 g button mushrooms
- 200 g gnocchi You could leave this out, but it does add a great texture
- 1 head garlic
- 20 g butter
- 2 Tbsp olive oil
On the side
- 4 baguettes
- 1/2 cup spring onions finely chopped
- 1/2 cup mozzarella grated
- Wipe or rinse the shiitake mushrooms and mushroom off-cuts to remove any grit.
- Reserve 1/2 cup of cold beef stock and whisk in the egg yolks. Set aside.
- Add the beef stock, fish sauce, pepper, shiitake mushrooms and mushroom off-cuts to a saucepan.
- Bring the stock and mushrooms to the boil then reduce to a simmer and simmer for 40 minutes.
- Strain the broth and check seasoning. Add salt if necessary.
- Set aside to cool a little.
- Smear the sweet potatoes and garlic in olive oil and roast in the oven for 1 hour at 180 deg. Instructions for roasting garlic.
- Brown the gnocchi in a little oil and set aside.
- Dice the button mushrooms and saute in 10 g butter until soft (about 7 minutes). Set aside.
- Clean and finely dice the leeks (the white and light green portion).
- Saute the diced leeks in 10 g butter until soft, about 10 minutes. Set aside.
- Allow the roasted sweet potatoes and garlic to cool a little after finished roasting.
- Peel the sweet potatoes then dice into 10mm x 10mm pieces.
- Squeeze the cloves of garlic out of the head, trying to keep them intact.
On the side
- Slice the baguettes length wise.
- Sprinkle with finely chopped spring onions and grated cheese.
- Bake in the oven at 180 degC until the cheese is melted.
- Stir the egg yolks into the broth and bring back to a simmer. The yolks will cause the broth to thicken a little.
- Add the diced sweet potatoes, leeks, button mushrooms, and gnocchi (if using) into the broth. Bring back to a simmer and simmer for 10 more minutes.
- Spoon the broth and vegetables into a bowl, add several cloves of roasted garlic, and serve with a baguette.