Place the butter in the pot, select Sauté, and adjust to More/High heat. When the butter has melted, add the shallot, sage, rosemary, and thyme and cook, stirring frequently, until the shallot is tender, 4 minutes. Add the broth and 1/2 teaspoon salt. When the liquid comes to a simmer, gradually whisk in the polenta. Press Cancel.
Lock on the lid, select the Manual or Pressure Cook function, and adjust to Low pressure for 8 minutes. Make sure the steam valve is in the “Sealing” position and that the “Keep Warm” button is off.
When the cooking time is up, let the pressure come down naturally for 15 minutes and then quick-release the remaining pressure. Unlock the lid and remove the pot from the appliance. Stir in the cheese, milk, parsley, and nutmeg. Season with salt and pepper.
Serve immediately as soft polenta, or transfer it to a container and refrigerate until solid. To reheat solid polenta, cut it into 1inch thick slabs and sauté them in olive oil in a nonstick pan over medium-high heat until crispy, 3 minutes per side.