Over the stove, heat a saucepan over medium-high heat and cook onion in oil for 3-4 minutes until tender. Add garlic and celery and continue to cook for a few minutes.

Once celery starts to soften, add beef and cook until no longer pink, 5-7 minutes.

Stir in fire roasted tomatoes and zucchini and cook 3-4 minutes, until tender.

Season to taste with salt and pepper. Add broth and thyme. Simmer mixture and allow to sit for 5-10 minutes.

Add cauliflower to boiling water and cook 8-12 minutes, until fork tender.

Drain cauliflower and dry on a towel for 5-10 minutes.

Add to a food processor or blender with remaining mash ingredients. Blend to combine until smooth (or mash by hand, if you prefer chunkier texture), seasoning to taste.

Preheat oven to 400°F (200°C).

Layer beef mixture into 9x13-inch casserole dish.

Pour mashed potatoes on top, smoothing out the mash to the edges of the dish in an even layer.

Bake until golden, around 20-25 minutes. Broil for 2-3 minutes to brown at the end, if desired.

For meal prep, cover uncooked keto shepherd’s pie casserole and store in the fridge for 2-3 days until ready to cook.

Line empty 9x13 casserole dish well with foil, using long enough pieces of foil to fold over the top of the dish once it’s filled.

Layer in keto casserole fillings.

Fold over excess foil and place entire dish in freezer overnight.

Once frozen, remove foil chunk from casserole dish. Return foil block to freezer with your casserole still in it and keep empty casserole dish to use as desired.

When ready to cook, transfer frozen foil-wrapped casserole back to casserole dish and thaw overnight in the fridge.

Remove foil from top of casserole and bake at 400°F (200°C) for 20-25 minutes, until golden. Broil for 2-3 minutes to brown at the end, if desired.