Preheat oven to 450°.
Slice the shallots, mushrooms, and 1 bunch of the basil.
In a saucepan, melt 2 tablespoons butter. Add the shallots and mushrooms and sweat over low heat for 10 minutes.
Add the wine and sliced basil. Over moderate heat, reduce by half. Add the stock and again reduce the liquid by half.
Pour in the cream and continue to reduce the sauce, over medium heat, until it has thickened. (It will coat a spoon rather heavily.) Strain sauce into a clean saucepan.
In a blender or food processor, purée the remaining basil (save a few nice leaves for garnish) with 1/2 cup of the sauce. Whisk the purée into the remaining sauce and, over low heat, finish by whisking in the remaining 8 tablespoons butter, one piece at a time. Taste and add salt if necessary. Strain and reserve.
Nap the bottom of each plate with sauce. Place the salmon escalopes on top of the sauce and cook in the oven or under the broiler for 1 minute, or until slightly underdone. Serve immediately.