Preheat oven to 375°F. Heat oil in large skillet set over medium-high heat; cook onion, celery, mushrooms, garlic, thyme, salt and pepper for about 5 minutes or until onion is slightly softened.
Add Quorn Meatless Pieces; cook for 2 minutes. Sprinkle flour over top; cook, stirring, for 1 minute. Slowly stir in broth and bring to boil. Reduce heat to medium-low; cook, stirring often, for 8 to 10 minutes or until sauce thickens slightly. Stir in mustard.
Meanwhile, on lightly floured work surface, roll out each biscuit into 6-inch round; repeat to make 10 rounds. Place each round in greased muffin cup, firmly pressing dough into bottom and up side of each muffin cup. Spoon filling evenly into each cup.
Bake for 18 to 20 minutes or until biscuits are golden brown. Let cool for 5 minutes; remove from pan. Sprinkle with green onions.
Tip: For a healthier version, add peas and carrots to the pot pies.