Instructions:
- Heat the broth in a small saucepan and keep it at a bare simmer on a back burner.
- Melt butter and oil in a large, heavy-bottomed Dutch oven over medium-high heat. Add onions and sauté until translucent (3-4 minutes). Add sliced mushrooms; cook without stirring initially to allow them to brown well, then sauté until deeply golden and moisture has evaporated (about 7-10 minutes).
- Push the mushrooms aside. Add the minced garlic to the empty space and cook for 30 seconds until fragrant. Add the dry orzo and toast, stirring constantly, for 1–2 minutes until the edges look slightly golden.
- If using wine, pour in the white wine. Scrape up any browned bits (the fond) from the bottom of the pan and let the wine bubble away completely until nearly evaporated.
- Add one ladleful (about 1 cup/240ml) of the hot broth to the orzo. Stir continuously until the liquid is almost completely absorbed. Continue adding the broth, one ladleful at a time, stirring frequently and allowing each addition to absorb before adding the next. This process should take about 15–18 minutes.
- The orzo is done when it is al dente and the mixture is creamy. Remove the pot from the heat.
- Stir in the fresh spinach in large batches until completely wilted down.
- Stir in the heavy cream, grated Parmesan cheese, and fresh lemon juice. Season aggressively with salt and freshly cracked black pepper.
- Cover the pot and let it stand for 2 minutes. Serve immediately, topped with extra Parmesan.