In a large pot with a tight fitting lid, heat the olive oil and butter over med-high heat. Once the butter has melted, add the onion to the pot and cook, stirring often, until translucent, about 3-5 minutes. Stir in the garlic and cook until fragrant, just another minute or so.

Stir in the orzo and let it toast for a couple of minutes. Increase the heat to high and stir in the broth and half & half. Once it reaches a boil, cover the pot with a lid and reduce the heat to med-low. Let this simmer for 5-7 minutes, stirring occasionally, until the liquid has mostly been absorbed by the orzo.

Remove the pot from the heat and immediately stir in the parmesan cheese (and the spinach if using). Then season to taste and serve immediately. Refrigerate any leftovers.