1. Toast cashews in skillet over medium-high heat 2 to 3 minutes, or until beginning to brown, shaking pan constantly. Transfer to bowl of food processor, and pulse until coarsely chopped.
2. Heat oil in skillet over medium-high heat. Add shallots, and sauté 3 to 4 minutes. Add mushrooms, and sauté 5 to 7 minutes, or until softened. Remove from heat, and cool 5 minutes.
3. Add mushroom mixture and red wine vinegar to cashews in food processor, and purée until nearly smooth. Season with salt and pepper, if desired, and serve warm or at room temperature.