Bring a medium saucepan of salted water to a boil and cook the potatoes until just tender, being careful not to overcook, 6 to 8 minutes. Drain, pat dry and spread in a single layer on a tray to cool. When ready to serve, heat the rajas in a medium saucepan over medium low heat, stirring frequently, just to heat through. Add the potatoes and stir occasionally until heated through. For potato and rajas tacos, toast 24 small Corn Tortillas and keep warm. For each taco, stack 2 tortillas and layer with the potato rajas mixture. Top with Salsa Fresca and an avocado slice and serve.
In a large skillet heat the oil over medium heat. Saute the onions with the salt and pepper until they begin to wilt and brown, 8 to 10 minutes. Stir in the julienned red peppers and chiles. Pour in the heavy cream, bring to a boil and reduce to a simmer. Cook 4 minutes or until the cream begins to thicken. Stir in the grated cheeses and remove from the heat. Serve immediately.
In a mixing bowl, combine all the ingredients. Stir and toss well, and serve. Store in a covered container in the refrigerator no more than 1 day.