In a medium pot, bring water and salt to a boil. Sprinkle in cornmeal while continually whisking until polenta thickens enough to bubble and pop. Lower heat and switch to stirring with a spoon or silicone spatula to prevent burning for a few more minutes, then cook uncovered, stirring every 5 minutes until polenta thickens and separates from sides of pot, 40 to 50 minutes. If it becomes too thick or clumps, incorporate a bit more water. Stir in butter until glossy and smooth. While polenta is cooking, work on the Brussels sprouts.
Preheat oven to 400 F. On two shallow baking pans, toss Brussels sprouts and red onion with oil, spread out in a single layer, and sprinkle with salt and pepper. Roast 12 to 18 minutes. When they’re close to desired doneness, toss, drizzle with 2 to 3 tablespoons balsamic vinegar, and top with feta and walnuts. Roast another 5 minutes.
Portion out polenta in bowls, top with roasted Brussels sprouts, and drizzle with some more balsamic vinegar.
NOTES: For crispy Brussels sprouts, follow the recipe as written. For more tender Brussels sprouts, use one baking pan and the vegetables will steam while roasting. For a meaty version, mix in some crumbled bacon or pair with chicken, beef, or pork tenderloin.
Per serving: 354 calories, 19 grams fat (6 grams saturated fat), 22 milligrams cholesterol, 342 milligrams sodium, 39 grams total carbohydrates, 7 grams fiber, 10 grams protein.
