What do you need:

500 g red potatoes, peeled and chopped
500 g ground beef
3 small white turnips, peeled and chopped
1 cup skim milk
2 tbsp. l. margarine (no trans fat)
1 large onion, finely chopped
1 cup frozen vegetables (green peas and chopped carrots)
2 garlic cloves, crushed
1 can chopped canned tomatoes
1/2 cup unsalted chicken broth
3 art. l. tomato paste
1 ч. l. finely chopped fresh thyme
1/4 ч. l. salt
1/4 ч. l. ground black pepper
What to do:

Put turnips and potatoes in a saucepan and fill with water 5 cm above the root crops. Bring to a boil over high heat. Then lower the heat, cover with a lid and let simmer for 20 minutes or until the vegetables are tender.
Drain the water, return the pot to the heat, add the milk and margarine, crush the turnips and mash potatoes. Cover with a lid and remove the pot from the stove.
Heat a frying pan over medium heat, put the minced meat, onions, garlic, carrots and peas in it and cook it all for 7 minutes or until the minced meat is a uniform brown color and the onions are soft.
Add tomatoes, broth, tomato paste, thyme, salt and pepper.
Reduce the heat and cook for 30 minutes, stirring occasionally, until the mixture thickens.
Spread the puree on top of the ground beef and serve.
If you want the mashed potatoes to be covered with a crispy crust, preheat the oven and send the pie into it for a couple of minutes or until the mashed potatoes are browned.