Both yacón (Polymnia sonchifolia) and topinambur (Jerusalem artichoke, Sunchoke, Helianthus tuberosus) have tubers composed mainly of inulin rather than starch. This is the part that is usually eaten, though young stems can also be eaten. Raw, these tubers are somewhat sweet and crunchy, but the skin has a stronger more resinous taste, so you might want to peel it. Because humans lack an enzyme to hydrolyze inulin, these vegetables pass through the body mostly unmetabolized, so they make ideal diet foods. I like them raw with lime juice and a sprinkle of salt as a snack, or sliced and sautéed as a dinner vegetable. They can also be baked or boiled, but they lose their crispness. I would not bake them in a pie. Oca (Oxalis tuberosa) can be bitter or sweet. The bitter varieties can contain up to 500 ppm oxalic acid (that's like spinach leaves). However, the sweet varieties contain only 79 ppm acid, which is 1/20 the amount found in a standard white potato. So, get a sweet variety; it'll be perfectly safe to eat. David E.