There are few things more comforting on a cold British afternoon than a bowl of mushroom soup. But the tinned stuff has a lot to answer for. A proper homemade version — deep, earthy, and enriched with cream — is a different creature entirely. The secret lies in two things: frying the mushrooms until they are genuinely golden, and finishing with fresh tarragon. That aniseed note cuts through the richness and makes the whole bowl sing.

Why golden mushrooms matter

Mushrooms are mostly water. If you slice them and throw them into a pan, they will first release that water and stew. That is not what you want. You want them to fry, to caramelise, to develop the savoury, almost meaty flavour that makes this soup so satisfying. So use a wide pan, get it properly hot, and do not crowd it. Cook in batches if necessary.

Use a mixture of butter and oil. The butter brings flavour, the oil stops it burning. Wait until the butter foams, then add the mushrooms with a good pinch of salt. Salt draws out water, but it also seasons. Keep the heat fairly high and resist stirring too often. Let them sit, then toss. After about eight to ten minutes they will squeak, then quieten, then turn golden at the edges. That is your signal.

Choosing your mushrooms

Button mushrooms alone make a thin, pale soup. They are fine as a base, but you need more. A mix gives complexity.

• Chestnut mushrooms — nutty and firm, they brown beautifully.
• Portobello or flat mushrooms — meaty and dark, they add depth.
• Dried porcini — a small handful, soaked in boiling water, transforms the stock. Keep the soaking liquid, strain it, and add it to the pot.
• Wild mushrooms — if you are lucky enough to find them, or buy them at a farmers' market, use them. They are seasonal and precious. Add them towards the end so they do not lose their character.

Avoid washing mushrooms if you can. Brush them clean with a damp cloth or a soft brush. If they are very gritty, a quick rinse and immediate drying is acceptable, but they will absorb water and take longer to fry.

The base, the liquid, and a little patience

While the mushrooms fry, soften a finely chopped onion in another pan with a knob of butter. Add two cloves of garlic, crushed, for the last minute. Do not let them colour. A stalk of celery, chopped small, is a good addition if you have it. When the mushrooms are golden, tip them in with the onions. Pour in a glass of dry sherry or white wine and let it bubble away to almost nothing. This deglazes the pan and adds a lovely acidity.

Now add your stock. Use a good chicken or vegetable stock — homemade if possible, otherwise a good quality cube. You need about 750ml to 1 litre, depending on how thick you like your soup. Add the strained porcini soaking liquid too. Bring to a gentle simmer and cook for 15 minutes. Do not boil hard or the flavour will flatten.

Cream, tarragon, and the finish

Take the pan off the heat. If you want a smooth soup, blend it now — but leave some texture. A few pulses of a stick blender is usually enough. Return to a low heat and stir in 150ml of double cream. Warm it through, but do not let it boil. Boiling cream can split and turn grainy.

Now the tarragon. Fresh tarragon is essential here. Dried tarragon is a poor substitute, tasting vaguely of hay. Strip the leaves from a few sprigs — you want about two tablespoons, chopped. Add them off the heat, just before serving. Stir them through and taste. Season with salt and plenty of black pepper. A small squeeze of lemon juice can sharpen everything if the soup tastes a little flat.

Serving and storing

Ladle into warm bowls. A swirl of cream, a few extra tarragon leaves, and a grinding of pepper. Serve with crusty bread — a sourdough or a warm baguette — or a cheese scone if you are feeling particularly British. A crisp green salad on the side is nice, but not necessary.

This soup freezes well, but do it before you add the cream and tarragon. Cool it quickly, pour into containers, and freeze for up to three months. Thaw overnight in the fridge, then reheat gently and finish with cream and tarragon as above. It will keep in the fridge for three days.

One final note: tarragon is a summer herb, but the soup is at its best in autumn when mushrooms are abundant. If you grow tarragon, pick it before the first frost. If you buy it, look for bright green leaves with no black spots. The aniseed flavour is what makes this soup memorable — do not skip it.