First make the polenta. Bring the chicken stock to a boil, add the salt and gently whisk in the cornmeal. Reduce the heat to low and cook until the cornmeal thickens, stirring frequently, about 15-20 minutes. (Note: The exact ratio of stock to cornmeal you will need will vary depending on the coarseness of the cornmeal.
If you are worried, start with 3 cups of stock and keep the other cup hot in a small saucepan and add until you have the consistency you desire.) Remove from the heat and add the butter, stir well until melted. Lightly oil a baking dish and transfer the hot polenta to the baking dish. Spread evenly, the polenta should be 1/2-3/4 inch thick. Refrigerate uncovered until firm, about 2 hours.
When the polenta is firm transfer it to a cutting board. Slice the polenta into the desired sizes. I like to use a round pastry cutter to create round slices of polenta, which looks nice but inevitably leads to waste - or what I like to call chef's treats. Cutting triangles would probably be just as visually appealing and less wasteful.
Slice the onion and peppers thin and then saute over medium heat in a couple tablespoons of olive oil, about 25 minutes. The peppers and onions should be soft and caramelized.
While the onions and peppers are cooking, slice the sausage links into 1 inch pieces and cook over medium-high heat, until well browned on all sides. When the sausage is almost completely cooked through, transfer it to the pan with the peppers and onions, including most of the sausage fat that has rendered in the pan (try to reserve about a tablespoon in the pan), toss well and reduce the heat to keep warm while frying the polenta slices.
In the saute pan that the sausage was cooked in, fry the polenta slices on medium-high heat until lightly golden and crispy, about 4-5 minutes per side. If there isn't enough sausage fat to fry all of the slices use olive oil to finish frying.
Serve the sausage and peppers over the polenta slices.