Step 1

Preheat the oven to 400 degrees F (200 degrees C).

Step 2

For the filling: Melt the butter in a large oven-safe skillet over medium heat. Add the carrots, celery and onion and season with salt and pepper. Cook, stirring frequently, until the vegetables begin to soften, about 6 minutes. Add the garlic and cook for 30 seconds. Add the beef or meat alternative. Increase the heat to medium-high and cook, breaking up the beef or meat alternative, until browned and cooked through, 5 to 7 minutes. Reduce the heat to medium, add the lentils and sprinkle with the flour; stir to combine.

Step 3

Whisk together the tomato paste and Worcestershire sauce in a medium bowl. Whisk in the mushroom or beef broth and add to the pan, scraping any stuck-on bits off the bottom of the pan. Bring to a boil, season with more salt and pepper if needed, then reduce the heat to low and simmer while you prepare the topping.

Step 4

For the topping: Cover the potatoes and garlic with a few inches of cold water into a large pot. Season well with salt and bring to a boil over medium-high heat. Once boiling, add the cauliflower, cover and cook until tender, 10 to 15 minutes. Drain and return to the pot. Using a potato masher or hand mixer, roughly mash the veg. Add the milk, butter and cream cheese and mash until the desired texture is reached. Season with more salt.

Step 5

Stir the frozen veg into the filling and remove from the heat. Top with the mash, spreading it into an even layer and scatter with the grated Cheddar. Transfer the pan onto a rimmed baking sheet just in case there is any bubble over and bake for until the cheese is melted and the top is lightly golden brown and crisp, 20 to 25 minutes.

Step 6

Allow the pie to cool slightly before serving.