Place a large, heavy-bottomed pot over medium heat and melt the butter until foamy but not browned. Add the diced onion and minced garlic, stirring often, and cook for 4–5 minutes until the onion turns translucent and smells sweet. Lower the heat slightly if the garlic begins to color.

Add the sliced mushrooms to the pot. The pan will look full at first, but the mushrooms will shrink as they cook. Stir occasionally and cook for 8–12 minutes until they release their liquid and develop golden-brown edges, which gives the soup its deep flavor.

Pour in the vegetable broth and add the thyme. Increase the heat and bring to a rolling boil, then reduce to medium-low. Simmer uncovered for 15 minutes, allowing the broth to darken slightly and the flavors to concentrate.

Remove the pot from the heat and let it cool for 2–3 minutes. Use an immersion blender to pulse the soup 4–6 times, breaking down some of the mushrooms while leaving a few chunks for texture.

Add the cottage cheese and blend continuously for 30–45 seconds until the soup is completely smooth and creamy. Season with salt and black pepper, tasting and adjusting as needed. The texture should be velvety, not heavy.

Ladle the hot soup into bowls, garnish with fresh chopped parsley, and serve right away while it’s steaming and fragrant.