Preheat the oven to 375°F and have ready a shallow casserole dish, at least 11 1/2 x 7 1/2 inches.
Prepare the enchilada sauce first: In a large, heavy-bottomed saucepan over medium heat, sauté the onions is oil for 4 to 7 minutes, until softened. Add the remaining sauce ingredients, bring to a simmer, and remove from the heat. When the mixture has cooled enough, taste and adjust the salt if necessary. Puree with an immersion or regular blender until the mixture is smooth and even.
Prepare the filling: Peel and diced the potatoes, then boil them until tender, about 20 minutes. Drain and set aside. Cook the grapeseed oil and minced garlic in a saucepot over medium-low heat, stirring occasionally until the garlic is sizzling and slightly browned (be careful not to let it burn). Add the kale, sprinkle with a little salt, and raise the heat to medium, stirring constantly to cover the kale with the oil and garlic. Partially cover the pot to steam the kale until it has wilted, 4 to 6 minutes.
Remove the lid and mix in the potatoes, vegetable stock, lime juice, pumpkin seeds, and salt. Use the back of a wooden spoon to mash some of the potatoes. Cook another 3 to 4 minutes, until the stock is absorbed. Add more salt or lime juice to taste.
Create an enchilada assembly line: Have ready a pie plate filled with about 3⁄4 cup of enchilada sauce, a casserole dish, a stack of corn tortillas, a lightly greased, heated griddle or cast-iron pan (for softening the tortillas), and the potato and kale filling.
Ladle a little bit of the enchilada sauce onto the bottom of the casserole dish and spread it around. Take a corn tortilla, place it on the heated griddle for 30 seconds, then flip it over and heat until the tortilla has become soft and pliable. Drop the softened tortilla into the pie plate filled with sauce; allow it to get completely covered in sauce, flip it over, and coat the other side.
Now, place the tortilla either in the casserole dish (the easiest way) or on an additional plate. Layer it with another heated, sauce-covered tortilla or just use one per enchilada; either way, run the potato filling down the middle and roll it up. Continue with rest of tortillas, tightly packing enchiladas next to each other.
Pour about a cup of sauce over the top (reserving some for later), cover tightly with aluminum foil, and bake for 25 minutes. Remove the foil and bake for another 10 to 15 minutes, until edges of the tortillas poking out of sauce look just a little browned. Allow to cool slightly before serving. Top individual servings with any remaining enchilada sauce, warmed slightly.