With stovetop burner set to medium, heat oil in pan until oil shimmers. Add mushrooms and onion. Cook until onions start appearing translucent and mushrooms start turning deeper brown (about 5 minutes).
Add ground beef and break up with spatula or wooden spoon. Cook until pink just disappears, about 5 minutes.
Add seasonings and garlic. Stir in and cook 90 seconds.
Add baby spinach. Cook until spinach shrinks to roughly half-size, about 3 minutes.
Add eggs. Let set for 1 minute, and then stir until eggs are scrambled and well-mixed.
Top with parmesan cheese. Let melt.
Serve with sourdough or other quality bread.