Prepare the cauliflower mash as directed, using a whole head of cauliflower. Dice the veggies for the mirepoix into equal sizes and keep them aside. Keep the frozen peas out in a strainer inside a bowl to defrost while you make the shepherd’s pie filling.
Heat a saute pan on medium heat and add olive oil and garlic. Add the trio of veggies and sautee for about five minutes until translucent. Add salt and pepper and herbs to your desired preference.
Add ground turkey to the vegetables and use a spatula to break the turkey into small pieces. While it cooks, use a flat-edged spatula to cut and loosen the meat. Cook for about 8 minutes or until the meat has browned.
Add chicken broth to the pan and bring it to a boil. Simmer for about 5 mins to absorb the flavours into the meat and vegetables.
Bring up the heat and add two tablespoons of tomato paste and two tablespoons of Worcestershire sauce. Mix it all up and cook on medium heat.
Mix the arrowroot starch with some liquid in a small bowl until combined, and stir it into the meaty gravy until it becomes thick. Switch off the heat immediately and stir in the drained peas. Add extra spices, salt and pepper for extra taste if required.
Transfer the meat filling into a 9×13 inch baking dish, and spoon the mashed cauliflower over it first, then use the back of a spoon or spatula to spread it evenly to cover the filling completely.
Make patterns with a fork on the mashed cauliflower, then bake the pie in the oven at 400°F for 10 minutes to warm up the mash. Turn on the broiler setting and broil the mash surface until it has browned on top. The cauliflower mash will puff up like regular mash.