Set oven to 400F.
Place cauliflower in a microwave safe bowl and cook in the microwave – according to instructions given – for 6 to 8 minutes, or until the cauliflower is soft. Set aside.
Set a large skillet on medium heat. Once hot, add oil, garlic, onion, mushrooms and celery and sauté for 2 to 3 minutes, then sprinkle in seasoning and cook for an additional 1 minute.
Add the meatless crumbles and chop it up as it cooks in the skillet. Continue folding the ingredients as they cook for 2 to 3 additional minutes.
Add lentils, tomatoes, frozen peas & carrots and fold everything together. Then add BBQ sauce and dijon mustard, and finally the veggie broth. Bring to a light simmer, then reduce the heat to low and cover and cook while you prepare the topping.
In a large bowl add the ingredients for the topping. Use a potato masher OR an immersion blender to whip together the cauliflower mash.
Remove the cover from the skillet and remove from the heat. Use a spatula to evenly spread the cauliflower mash on top, then use the back of a fork to spread it out to create a textured top.
Place the shepherd’s pie in the oven to bake for 20 minutes.
After baking let it cool down for 15 to 20 minutes, then garnish and enjoy!