Preheat your oven to 350 degrees.

Put a large pot of water on to boil, then roughly chop the russet potatoes. When you've finished chopping, add them to the pot (yes, even if the water isn't yet boiling) and cover.

While the potatoes begin to boil, roughly chop the florets off a head of cauliflower. Place them in a colander and then submerge the colander into the potato pot so that you can cook both the cauliflower and the potatoes at once, but remove them at different times since the cauliflower takes longer to cook. (Alternately, you can cook the cauliflower in a different pot.) Cook both until tender - approximately 15 minutes for the potatoes and 20 minutes for the cauliflower - then drain.

While your potato/cauliflower pot boils, begin heating a non-stick saute pan while dicing 1/2 onion. Add that to the pan and toss every few minutes until browned, then remove to the casserole dish.

Add 1 pound of lean ground turkey to the empty saute pan, and season with salt, pepper, garlic, and 1 tbsp ground rosemary. Use a spoon to periodically break up the turkey as it browns, so that you get a fine mash instead of large chunks.

While the turkey browns, dice 1 large carrot and 2 stalks celery, adding them to the pot as you go. Add the onions back to the pot, and then add 1/2 cup plain tomato sauce. Stir to incorporate, and then add one 12 oz bottle of your favorite cider - I used Woodchuck Amber, to add a little sweetness but not too much. Add about 1/2 cup of the starchy potato water (pouring it without measuring is fine), then cook for about 15 minutes to reduce down.

Once the cauliflower and potatoes are each tender, drain and then put them back in the pot. Season with salt, pepper, and garlic, then mash them together with a potato masher. You may also need to use a spoon to cycle through and be sure you thoroughly mash any bits of cauliflower, especially if you weren't diligent about using the florets only and discarding the stems.

Once the saute an has reduced down to a thick meat sauce, pour into a 9x9 square casserole dish. Use a spoon to smooth out the layer, then top with the cauliflower/potatoes. Finally, generously grate some low-fat Irish cheddar on top, and bake in the oven at 350 degrees for 30 minutes, or until the cheese is gooey and bubbly.

Let cool (so it doesn't burn your mouth!), then cut into squares and serve.