Heat oven to 400. Set a 10"-deep dish pie pan on a baking sheet. Bring parsnips, carrots and sweet potato to a boil in lg pot over high heat. Reduce heat to medium-low. Cover, simmer for 10 min, drain, cool. Melt butter in lg skillet over medium heat. Add mushrooms and leeks, cook until tender. Whisk in flour until mix thickens slightly. Gradually whisk in broth, thyme, salt, pepper and hot sauce. Add veggies to mix. Spoon mix into pie pan. In bowl, combine biscuit mix and milk, mix well. Drop by heaping tbsp of batter over pie filling. Bake until top is browned, about 20 min.