I recommend cooking the carrots with the onion. Otherwise they are a bit crunchy.

2 sweet potatoes, peeled and cubed
1/2 cup low-fat plain greek yogurt
Sea salt
Fresh ground black pepper
2 teaspoons olive oil
1/2 cup yellow onion, chopped
2 cloves garlic, chopped
1 lb bonesless, skinless chicken breast, cubed
2 tablespoons whole-wheat flour
1 teaspoon dried marjoram (or poultry seasoning)
1 cup low-sodium chicken broth
1 tablespoon Dijon mustard
1 cup carrots, peeled and sliced
1 cup frozen peas

2 sweet potatoes, peeled and cubed 1/2 cup low-fat plain greek yogurt 2 teaspoons olive oil 1/2 cup yellow onion, chopped 2 cloves garlic, chopped 1 lb bonesless, skinless chicken breast, cubed 2 tablespoons whole-wheat flour 1 teaspoon dried marjoram (or poultry seasoning) 1 cup low-sodium chicken broth 1 tablespoon Dijon mustard 1 cup carrots, peeled and sliced 1 cup frozen peas

1. Preheat oven to 350.
2. In a medium saucepan, add sweet potatoes and enough cold water to cover. Bring to a boil and cook for 10 minutes, intil fork-tender. Drain and transfer to a food processor with greek yogurt and sea salt and pepper, to taste. Puree until smooth and set aside.
3. In a large skillet, heat olive oil on medium-high. Add onion and garlic and cook, stirring occasionally, until soft, about 2 minutes. Add chicken breast and cook, stirring frequently, for 3 minutes, until golden brown. Add flour and marjoram and stir to coat. Add check broth and mustard and bring to a simmer. Cook, stirring frequently, for 1 to 2 minutes, until sauce thickens. Remove from heat and stir in peas and carrots. Add additional salt and pepper to taste.
4. Spoon mixture into a 9-inch pie dish, spreading evenly over bottom. Spread sweet potato mixture over top, smoothing with the back of a spoon. Bake for 20-25 minutes, until filling is bubble and top is golden brown.