This is a great casserole that will have you making this for dinner every week.
Heat oven to 400ºf.
In a large pot on medium heat cooking oil. Add onions and red pepper. Cook for about 5-6 minutes until translucent stir intermittently. Add garlic and cook until fragrant. About 2 minutes.
Next add the sausage and cook for another 5-6 minutes until sausage starts to brown. Stir constantly. So it does not burn. Add the sauerkraut, white wine, thyme and pepper and stir until combined. Cook for about 10-12 minutes stirring occasionally until most of the liquid is evaporated.
Transfer the Ukrainian sausage mixture to a greased 9 x 13 casserole dish. Spread the Greek yogurt even over top the mixture. Spread the mashed potatoes over top the sausage mixture. Top with the grated cheese.
Put casserole dish in the oven and bake for about 22-25 minutes until golden brown. Remove from oven and let cool for 5- 10 minutes.