For the Polenta:
Bring the water to a boil in a heavy-bottomed saucepan. Whisk in the polenta, stirring constantly for the first minute or so. Reduce heat to low and continue cooking, stirring frequently, for about 30 minutes, or until the polenta thickens. (You may need to add a few tablespoons of water if the polenta gets too thick.) Stir in the butter and cheese, and keep warm until ready to serve.
For the Roasted Pepper Salsa:
Brush all the peppers with a tablespoon of the olive oil and roast over an open flame (or on a sheet pan 3 inches from a hot broiler in the oven), turning occasionally, until blackened on all sides. Place the hot peppers in a bowl large enough to hold them all, cover with plastic wrap, and set aside for about 15 minutes. (This will allow the skins to peel off more easily and the peppers to cool enough to handle.) Peel and seed all the peppers and cut the flesh into small dice. Heat another tablespoon of the oil in a skillet over medium-low heat. Add the sweet onion and cook and stir until slightly brown, about 8 minutes. Remove from heat. When cool, stir in the diced peppers, five spice and vinegar, then season to taste with salt and pepper.
For the Halibut:
In a heavy skillet, heat the remaining tablespoon of oil over medium-high heat. Pat the halibut pieces dry with paper towels and season with salt and pepper. When the oil shimmers, add the halibut and cook until caramelized, about 5 minutes on the first side and 3 on the second side. (Timing depends on the thickness of your filets—the halibut will lift easily off the pan when it's done. Fight the urge to peek at it before then.)
To serve, divide the polenta between four shallow bowls, top with the pea shoots, then the halibut. Spoon the salsa over the top and garnish with additional Parmesan.