Step 1

If you have an Instant Pot you may use this Instant Pot method to make your mashed potatoes. If you don't have an Instant Pot, add your quartered potatoes to a pot and fill with salted water, covering 1 inch above the potatoes. Bring to a boil, and then lower heat to maintain a low boil and cook until fork-tender. Approx. 15-20 minutes. Once cooked, drain and return the potatoes to the pot. Mash them using a potato masher, add the milk and mix well. Taste for salt, add more if necessary, and set aside.

Step 2

Meanwhile, sort through your lentils, discarding any small rocks, and rinse them well in a colander. Then place the lentils with 4 cups of water and a teaspoon of salt (or use broth for added flavour) in a small saucepot. Bring to a boil, then reduce heat and simmer for 20-22 minutes. Don't overcook your lentils as they'll continue cooking in the oven. Drain and set aside.

Step 3

Use a large, deep pan to sauté the onion, carrot, celery, and garlic until soft, approx. 7-10 minutes. Then add the mushrooms and cook until reduced, approx. 5 more minutes.

Step 4

While the veggies are sauteéing, use a bowl or large measuring cup to whisk together the 2 cups of broth, flour, balsamic, red wine, thyme, and sage. Then pour it into the pan with the sautéed veggies. Cook, stirring often until your gravy is slightly thickened, approx. 5 minutes.

Step 5

Preheat the oven to 400 degrees F. Then transfer the cooked lentils and sautéed vegetables with the gravy to your casserole dish and mix well. Top with the mashed potatoes and use a fork to create a crisscross pattern, if desired. This will make the top layer crispier when baking. (See process shots above.)

Step 6

Bake your pie for 20-25 minutes, until the top is golden brown. Then remove from the oven and let rest for a few minutes before serving.