Cover potatoes and garlic with water in a pot and bring to the boil. Cook for about 15 minutes or until potatoes are very tender. Add beans and return to the boil for 1 minute. Drain well and return to pot.
Using a potato masher, add milk and mash potatoes and beans until smooth; set aside and keep warm.
In a large nonstick skillet, heat oil over medium heat and cook onion, carrot and celery for about 5 minutes or until softened. Add turkey, thyme and pepper; cook, stirring for about 4 minutes or until turkey is browned.
Add flour and cook, stirring until flour is absorbed. Add broth, tomato paste, Worcestershire and bay leaves; bring to a boil. Reduce heat and simmer, stirring occasionally for about 8 minutes or until thickened.
Remove bay leaves and pour mixture into an 8 cup (2 L) casserole dish. Spoon potato mixture over top to cover evenly.
Bake in a preheated 400 F (200 C) oven for about 20 minutes or until potatoes are lightly golden and filling is bubbling.