Heat oil and 1 tbsp butter in a large pot over medium-high heat. Add mushrooms in a single layer, cook undisturbed 4 minutes, stir, and cook 4 more minutes until golden.

Reduce heat to medium, add remaining 1 tbsp butter, onion, and a pinch of salt. Cook 3 minutes until soft. Add garlic and cook 1 minute.

Sprinkle flour over the vegetables and stir 2 minutes. Slowly whisk in broth, bring to a boil, then reduce heat and simmer 10 minutes until slightly thickened.

Remove from heat and blend with an immersion blender until smooth. Stir in cream, return to low heat, and warm 2 minutes without boiling. Season with salt and pepper.

Ladle into bowls, top with thyme and a crack of pepper. Serve hot.