Preheat oven to 400 degree F.
Finely shred sweet potato in either the food processor or box grater; place shredded potato in a bowl; set aside
Whisk together eggs, milk, garlic powder, salt and pepper; set aside
Using a clean kitchen or tea towel, wring out the shredded potato to remove excess moisture. In a medium bowl, using a spatula, gently mix in arrowroot flour. Once combined, place shredded potato into greased (I use Chosen Foods Avocado Oil Spray) muffin tins (making about 12 small muffins). Press the potato down, ensuring that it bakes evenly. Bake for 15 minutes, or until edges are slightly browned.
While the potatoes are baking, heat olive oil on medium-high heat and sauté onions for 2-3 minutes, until translucent. Add spinach and allow to wilt, about 1-2 minutes; set aside and allow to cool (if it's too hot, it will start to cook the eggs).
Once the potatoes are ready, spoon spinach and onion mixture evenly into muffin tins, followed by evenly pouring in the egg mixture. Finally, sprinkle with chopped prosciutto.
Bake for 15-17 minutes, or until the top of muffin is no longer runny and prosciutto is crispy.
Carefully, run a knife along the side of each muffin (while in the pan), making it easier remove. Serve warm or at room temperature - both are delicious!