Bring a small pot of water to a boil, carefully lower the large egg into the water, and cook for 6.5 minutes. Immediately transfer to an ice bath, peel when cool, and set aside.
In a medium saucepan over medium heat, melt the ghee. Add the sliced cremini mushrooms and sauté until browned and tender, about 5-7 minutes.
Add the bone broth, sea salt, black pepper, thyme, and rosemary to the saucepan with the mushrooms. Bring to a gentle simmer.
Stir in the rolled oats and cook for 5 minutes, stirring occasionally until the liquid is mostly absorbed.
Slowly pour the liquid egg whites into the oats while whisking constantly. Continue to cook for 2-3 minutes until the porridge is thick and creamy.
Fold in the fresh spinach and nutritional yeast, stirring until the spinach has wilted.
Transfer the porridge to a bowl, slice the soft-boiled egg in half, and place it on top before serving.