Heat the avocado oil in a large skillet over medium-high heat. Add the ground beef and cook, breaking it into small pieces, until browned.
Add the onion and cook for 2–3 minutes, until it begins to soften.
Add the mushrooms and cook until they release their moisture and begin to brown. Avoid overcrowding the skillet so the mushrooms brown rather than steam.
Add the garlic and cook for about 30 seconds, just until fragrant. Season with salt and black pepper.
Stir in the dry orzo and tomato sauce until well combined.
Pour in 1¾ cups water and stir. Bring to a boil.
Reduce the heat to low, cover, and simmer, stirring frequently, until the orzo is tender. Uncover toward the end and continue cooking until the remaining liquid is fully absorbed or evaporated.
Remove from the heat and let rest for a few minutes. The orzo will thicken as it sits.
If your skillet is oven-safe, leave the orzo in the skillet. Otherwise, transfer it to an oven-safe baking dish. Top evenly with the shredded mozzarella.
Broil for 2–4 minutes, watching closely, until the cheese is melted, bubbly, and lightly golden.
Let rest for 5 minutes before serving. Bon appétit!
Watch the texture rather than the clock. Orzo can absorb liquid differently depending on your skillet and heat. If there is still liquid once the orzo is tender, uncover and continue cooking, stirring frequently, until the mixture is thick and the excess liquid has evaporated.
Using an oven-safe skillet keeps this truly one-pan, taking the orzo straight from the stovetop to the broiler. If you don’t have one, simply transfer the orzo to an oven-safe baking dish before adding the cheese.
Make it yours
For a richer flavor, replace the water with beef broth.
Add a pinch of red pepper flakes if you like a little heat.
Mozzarella gives the dish a mild, bubbly topping, but provolone, fontina, or Monterey Jack are great alternatives.
For a sharper finish, try white cheddar.
At the table
Serve hot while the mozzarella is bubbly and golden.
A simple salad or a cacik makes a fresh, crisp side for this hearty dish.