In a frying pan, melt butter over medium heat, add onions, mushrooms, and sauté for 10 minutes, until onions are translucent, and mushrooms are soft and browned.
Add garlic, Worcestershire sauce, and thyme, mix well. Then add spinach sauté, for 3 minutes, until wilted.
Add Riced Cauliflower, broth and mix well. Increase heat to bring to a simmer, occasionally stirring, cook for 5 minutes, until rice is soft, and liquid is absorbed.
Reduce heat to low, add cream, parmesan cheese, constantly stirring for 2 minutes, until cheese is melted, and sauce is smooth and thick. Add salt, and pepper, mix well. Remove from heat and ready to serve.