1 (4-ounce) piece of pancetta, diced into 1/2-inch pieces
1/2 medium yellow onion, finely chopped
1 teaspoon finely chopped fresh thyme leaves
1 3/4 cups orzo pasta (about 11 ounces)
2 1/2 cups water, plus more as needed
1 1/2 cups milk (not nonfat)
3/4 teaspoon fine salt, plus more for seasoning
1/4 cup finely chopped fresh Italian parsley
2 tablespoons grated Parmesan cheese
Heat a Dutch oven or large, heavy-bottomed pot over medium heat until hot, about 3 minutes. Add the pancetta and cook until the fat starts to render out, about 1 minute. Add the onion and thyme and cook, stirring occasionally, until the onion is softened, 5 to 6 minutes.
Add the orzo and cook, stirring occasionally, until lightly toasted and fragrant, about 2 minutes. Add 2 1/2 cups water and scrape up any browned bits from the bottom of the pan with a wooden spoon. Add the milk and 3/4 teaspoon salt, stir to combine, and bring to a boil.
Reduce the heat to medium-low and simmer uncovered, stirring often and making sure to scrape the bottom and corners of the pan with the wooden spoon, until almost all of the liquid is absorbed and the orzo is tender, about 10 minutes. (Depending on the brand of orzo, you may need more liquid, so add more water, 2 tablespoons at a time, if all of the liquid is absorbed but the orzo is not tender yet; you want the final mixture to be creamy, but not clumpy and gluey.)
Remove the pot from the heat and stir in the parsley and Parmesan. Taste and season with more salt as needed. Serve immediately.