1. Melt butter with olive oil in a pot over medium-high heat. Add mushrooms; cook until browned and their liquid evaporates, 6–8 minutes.
2. Add onion, a pinch of salt, and cook until translucent, 3–4 minutes. Stir in garlic and thyme; cook 30 seconds.
3. Pour in broth and bring to a boil. Add orzo; simmer, stirring occasionally, until just tender, 8–10 minutes.
4. Lower heat; stir in cream and soy sauce. Simmer 1–2 minutes to thicken slightly. Season with salt and lots of black pepper.
5. Rest 2 minutes (orzo continues to hydrate). Ladle into bowls and garnish with parsley and thyme.