2Prepare the dough by blending cream cheese and butter until uniform and smooth.
3Blend in biscuit mix until mixture resembles coarse crumbs. Add milk in a slow steady stream until a soft dough forms.
4Gather dough and place on a lightly floured rolling surface. Roll the dough out into large rectangle 1/2" thin and 12"x14" wide. Cover dough until ready to fill and roll.
5Prepare filling by spraying a baking sheet with pan release.
6Sauté onions and mushrooms in 3 tablespoons butter until just tender.
7In a large bowl, combine onion/mushroom mixture, salt, pepper, chicken, tarragon and parsley. Stir in eggs, Swiss cheese and cooled gravy.
8With long side facing you, spread chicken filling just off center (lengthwise) of dough. Beginning with closet edge of dough, roll dough to enclose filling. Tuck ends under to prevent filling from baking out.
9Place strudel on prepared baking sheet, seam side down. Make shallow slashes on top of dough every 2". Brush with melted butter.
10Bake in oven until crust is golden brown and filling is just beginning to bubble, about 45-50 minutes.
11Let strudel stand for 5-8 minutes before slicing into serving pieces. For best slicing results use a serrated knife.
12Garnish with a dollop of whipped cream and fresh parsley.