Start by heating the olive oil in a large skillet over medium heat. Add the chopped onions and cook until translucent, about 5 minutes. Stir in the mushrooms, season with salt and pepper, and cook for another 3 minutes. You’re building the savory base for the dish here.
Melt the butter in the skillet before adding the orzo, broccoli florets, and fresh thyme leaves. Stir frequently for about 5 minutes to lightly toast the orzo, enhancing its nutty flavor. The broccoli gets a head start on cooking and maintains some crunch.
Pour in the white wine and stir as it simmers for about a minute. Add the vegetable broth, bay leaf, garlic powder, and cayenne pepper, then cook and stir occasionally for another 8-10 minutes until the orzo absorbs most of the liquid.
Once the orzo is al dente, mix in the lemon zest and milk for added creaminess. Stir in half of the shredded cheddar and manchego cheese until it melts into the dish, creating a gooey, cheesy result.
Preheat the oven to 425°F. Top the skillet with the remaining cheese and bake in the oven for 10-15 minutes. For a bubbly golden finish, switch to broil for the last 2 minutes—but watch closely to avoid burning.
Remove the skillet and scatter fresh basil across the top. Serve it warm and enjoy all that cheesy, creamy goodness!