In a heavy bottomed saucepan, melt butter over medium-high heat. Add garlic, shallots, rosemary, and red pepper and saute until vegetables are tender. Add all liquid and bring to a boil. Slowly pour in polenta, whisking constantly. Continue to stir for about 3 to 5 minutes and then add Parmesan and parsley and season, to taste, with salt and pepper. Pour onto a half-sheet pan and cool. (You can make the polenta the day before and store in refrigerator.)
Cut cooled polenta into 4 by 4-inch squares and then cut each in half to make triangles. When ready to prepare salmon, lightly oil a flat grill or grill pan; when hot, place polenta triangles in pan and brown on both sides, in batches as needed.
Heat olive oil in a large skillet and add garlic and onions. Saute until golden brown, then add mushrooms and saute until tender. Deglaze with white wine. Reduce until little liquid remains and then stir in 2 tablespoons cold butter. Season, to taste, with salt and pepper. Keep warm until ready to serve.
Heat a grill or grill pan. Lightly oil the salmon fillets and season with salt and pepper. Place on grill, skin side up, and cook for 3 to 4 minutes. Flip over and cook for 3 to 4 more minutes. Remove from grill and serve promptly with a portion of the ragout and 2 polenta triangles per person.
Cook's Note: For best flavor, moisten some alder chips and place inside a can in your grill while cooking salmon.