1. Put potatoes in a medium pot and add just enough water to cover, plus a pinch of salt. Bring to a boil, covered; add wakame, reduce heat to low, and simmer until potatoes are tender when pierced with a knife, about 20 minutes. Drain, saving about 1/2 cup cooking liquid.
2. Meanwhile, in a large frying pan, sauté onion in oil over medium-high heat until softened, about 6 minutes. Add garlic and dulse; reduce heat to medium and cook, stirring often, 3 minutes more. Add potatoes and heat for a few minutes, stirring gently to combine. Pour in some cooking liquid to moisten if you like. Season with salt to taste.
*Find wakame at Whole Foods Markets or Japanese markets; dulse is available at Whole Foods (both are types of dried seaweed). Or order them from Ocean Harvest Sea Vegetable Company (ohsv.net or 707/937-1923) in Mendocino, California.
Note: Nutritional analysis is per serving.