Heat a large fry pan or wide bottomed pot on medium.

When warm add the olive oil and the mushrooms, thyme and salt and gently sauté. The mushrooms will soak up the olive oil, so now add the butter and keep stirring till they are softening and cooking. Don't let them brown up. If there are large pieces that are still not cooking add a couple of tablespoons of stock ( or water) and keep stirring till the mushrooms are soft and the liquid is evaporated.

Pour the mushrooms into a food processor and add the dijon mustard, the sour cream and grated pepper ( you may need a little more salt but combine and taste first)

Whizz till nice and fine then taste. You can add a bit of cream or more dijon or salt. Its up to you. I liked mine just how it was. It will now combine with lots and lots of other flavours ( see above for ideas)

*** Note . don't add too much sour cream if you want to cook with it. Better to add cream as cream works with heat much better.