Preheat the oven to 400 degrees. Line two baking sheets with parchment.
Lightly brush both sides of the sweet potato planks with olive oil and season with salt and pepper. Place them on one of the prepared baking sheets and roast for 25 minutes, turning once after 15 minutes, until the potatoes are tender (but not mushy) and lightly browned.
Place the prosciutto slices on the second prepared baking sheet and pop it in the oven along with the sweet potatoes for 8-12 minutes (depending on the thickness of your prosciutto) until lightly browned and crisp. (Keep an eye on it during the last few minutes of cooking time—it will go from brown to burnt very quickly!)
Meanwhile, prep the avocado mash. Scoop the flesh from the avocado into a medium bowl. Add the lemon juice, a pinch of salt, and the crushed red pepper flakes (if using), and mash with a fork until the avocado is relatively smooth.
Assembly time! Spread each sweet potato “toast” with one quarter of the avocado mash. Add a slice of crispy prosciutto and top with the cherry tomatoes, Parmesan, and chives. Serve topped with poached or fried eggs if you like.