Steam or microwave the cauliflower until it is mushy.
Using a blender, blend the cauliflower with a bit of salt, pepper. Add the sour cream one tablespoon at a time until the texture resembles mashed potatoes. Set aside.
Heat a sauté pan. When hot, add one teaspoon of olive oil. Toss in the onions and mushrooms. Add salt, pepper, garlic, and ginger to taste, actually go a little overboard with everything. Toss a few times, cover, and reduce heat to low. Stirring every now and again, cook until onions are translucent.
Raise to medium-high heat and add the ground turkey. At this point, you will be happy that you went a little over the top with the spices, as you will not be able to adjust the seasoning with all that raw turkey meat abounding. Cook until most of the pink is gone.
Into a deep 8" baking dish, dump the turkey sauté and spread out evenly. On top of the turkey, layer the peas. On top of the peas, spread on the mashed cauliflower making sure that it is complete covering everything.
Cover with foil and cook at 375 °F (190 °C). After 30 minutes, remove the foil and place under the broiler for another few minutes to brown the cauliflower.
Remove from the oven and let sit for 10 minutes. Note: add the salt, pepper and seasoning to taste, don't be literal with the amounts listed.
There are 283 calories in 1 serving of Turkey and Cauliflower Shepherd's Pie.