In large saucepan, heat oil over medium heat; cook mushrooms, salt, thyme, savory and pepper, stirring often, for 5 minutes.
Add squash, potatoes and 1 cup of the beef stock; bring to boil. Reduce heat to medium-low; cover and simmer for 10 minutes.
Add Beef Base; bring to boil. Whisk flour with remaining stock; stir into pan and cook over medium heat, stirring often, until thickened, about 5 minutes.
Meanwhile, trim beans; cut into 1-inch pieces. Add to pan and cook, covered, until tender-crisp, about 5 minutes. Pour into 13- × 9-inch glass baking dish; set aside.
Biscuit topping: in bowl, combine flour, baking powder and salt. Using pastry blender or 2 knives, cut in shortening until in coarse crumbs. Add milk all at once, stirring with fork to make soft, slightly sticky dough. Turn out onto lightly floured surface; knead gently 10 times.
Pat out dough to 13- × 9-inch rectangle; cut into 12 squares. Using spatula, place on filling. Bake in 450 F oven until bubbly and topping is no longer doughy underneath, about 20 minutes.