In a large skillet over medium-high heat, melt 6 tablespoons butter with 1 tablespoon olive oil. Add pork and cook until golden brown, about 8 minutes. Transfer pork to vegetable mixture, reserving skillet. Add tomato paste to pork and vegetable mixture and cook 2 minutes. Meanwhile, add Marsala to reserved skillet and bring to a boil, stirring with wooden spoon or spatula, scraping up all the browned bits from bottom of pan. Pour Marsala over pork and vegetable mixture, place saucepan over medium-high heat, and bring to a boil. Immediately reduce to a simmer and cook until liquid has reduced by one-third, 30 to 45 minutes. Add chicken stock, herb bundle, and mushroom soaking liquid (if using); stir to combine. Bring to a boil, reduce heat, and let simmer, partially covered, for 2 hours. Remove from heat, season with salt and pepper; set aside to cool. Remove herb bundle.