Heat oven to 350ºF.
In a large, oven-safe saucepan set over medium heat, heat the olive oil. Add the red onion and salt and sweat until the onions begin to turn translucent, 4 to 5 minutes. Reduce the heat to low, add the garlic, and saute for 1 to 2 minutes, making sure the garlic does not burn.
Turn the heat up to high, add the chicken stock, bring to a boil. Gradually add the cornmeal while continually whisking. Once you have added all of the cornmeal, cover the pot and place it in the oven. Cook for 35 to 40 minutes, stirring every 10 minutes to prevent lumps.
Once the mixture is creamy, remove from the oven and add the butter, salt, and pepper. Once they are incorporated, gradually add the Parmesan.
Serve as is, or pour the polenta into a 9-by-13-inch pan lined with parchment paper. Place in the refrigerator to cool completely.
Once set, turn the polenta out onto a cutting board and cut into squares, rounds, or triangles. Brush each side with olive oil and saute in a nonstick skillet over medium heat, or grill.