Place peeled and diced potatoes into a medium saucepan and add enough water to cover the potatoes by at least an inch. Bring to a boil over high heat, then immediately reduce the heat to medium-low and simmer until the potatoes are tender and can easily be pierced with a fork.

Drain the potatoes then place them in a medium-sized mixing bowl. Add the butter, sour cream, salt and onion powder, and then whip until light and fluffy, using a hand mixer. Cover the bowl and set the potatoes aside while you make the filling. Preheat the oven to 375 degrees and spray a 2-qt casserole dish with cooking spray and set aside.

Place a large pot over medium-high heat and melt butter. Add onion, carrots, celery and garlic and cook for 7–8 minutes, stirring frequently. Add thyme, savory, bay leaves, vegetable broth (or water) and lentils and stir to combine. Allow the liquid to come to a boil, then reduce the heat to low, cover and simmer for 20 minutes, stirring occasionally.

After 20 minutes, remove the lid and test the lentils. Continue simmering, uncovered, until the lentils are tender. (Do not add any salt until the lentils have tenderized.) Once the lentils are tender and the mixture has thickened substantially, add the tomato paste and soy sauce and stir until the tomato paste is completely combined. Taste the lentils for seasoning and add additional salt and pepper if necessary. Remove and discard both bay leaves.

Transfer the lentil mixture to the prepared casserole dish and top with the whipped potatoes. Brush the top of the potatoes with beaten egg and bake uncovered for 25–30 minutes or until the tips of the potatoes turn golden brown and the filling is bubbly. Remove from oven and cool for 10 minutes before serving. Enjoy!