Make the polenta: Bring the chicken stock to a boil in a large pot. Add the polenta and whisk until fully incorporated, 3 to 4 minutes. Sprinkle with 1/2 teaspoon salt; cover and cook over medium heat, 5 to 6 minutes. Finish by folding in the melted butter. Keep warm.
Make the chorizo sauce: Coat a large saute pan with the olive oil and set over medium-high heat. Add the onion and cook, stirring, until almost translucent, about 10 minutes. Add the ground pork and brown 4 to 5 minutes, breaking it up with a wooden spoon. Add the paprika, granulated garlic, onion powder, chili powder and cumin and sprinkle with 1/2 teaspoon salt and 1/4 teaspoon pepper. Cook 1 more minute to toast the spices, then add the vinegar, minced garlic and tomatoes. Simmer until the sauce is thickened and reduced, about 15 minutes. Taste and season once more with salt and pepper. Keep warm.
Make the lasagna: Wash, drain and finely slice the chard. Heat the olive oil and garlic in a large skillet over medium-high heat; add the chard and saute 3 to 4 minutes. Season with salt and pepper. Drain in a colander and squeeze out any excess moisture.
Preheat the oven to 350 degrees F. Lightly oil a 9-inch-oval or 8-inch-square flameproof baking dish. Pour half of the polenta in the dish and spread out evenly. Top with half of the chorizo sauce and all of the chard. Sprinkle with half of each cheese. Top evenly with the remaining polenta, then the remaining chorizo sauce and finally the remaining cheese. Cover with aluminum foil, place the dish on a sheet tray and bake 30 minutes. Turn on the broiler. Remove the foil and broil until the cheese is golden and bubbly, about 3 more minutes. Let sit for 25 minutes before serving.