Heat the oven to 375 degrees.
Prepare 1/2 Batch of Stiff Mashed Potatoes https://www.roguechef.com/?recipe=stiff-mashed-potatoes-reboot.
Or make a whole batch and freeze
Melt the butter in the 10-inch skillet over medium-high heat
Add the mushrooms and cook, stirring often, until they start to take color, about 6 to 8 minutes. Add onions and cook until they are translucent, 5-6 minutes, add garlic and cook until fragrant, ~ 2 minutes
Deglaze with broth
Reduce the heat to medium and add broth, carrots, carrots, rosemary, thyme and continue to cook until tender, and broth reduces, another 10 minutes
Season to taste with salt and pepper. Add the tomato paste and stir, cooking until it is well combined, another 2 to 3 minutes
Sprinkle flour over the mixture, stir and cook for 1 minute. Add the heavy cream and peas, cook to thicken. 2-3 minutes
Transfer the veggie stew into a 3 qt casserole, and top with potatoes. Sprinkle with Parmesan.
Place casserole on foil lined sheet pan
Transfer to the oven and. Bake the pie until the potatoes have begun to brown and the edges are bubbling, about 30 minutes. Let stand at room temperature for 15 minutes before serving.