In a 12 to 14-inch saute pan, heat the olive oil over high heat until almost smoking. Add the onion and garlic and cook over medium-high heat 5 minutes, until soft and light golden brown. Add the chard and saute over high heat until very soft and tender, about 10 minutes. Remove from the pan and press under a plate to remove excess moisture. Finely chop the Swiss chard.
Preheat oven to 350 degrees F.
Place the chard mixture into a mixing bowl and add the besciamela, eggs and yolks, ricotta and 1/4 cup Parmigiano and season with nutmeg and salt and pepper.
Butter a bundt cake pan and sprinkle with bread crumbs to coat. Pour the mixture into the pan, and place the pan in a roasting pan. Carefully pour cool water into the roasting pan to come up 3 inches on the side of the bundt pan and place in the oven. Cook until the custard is just cooked through, about 35 minutes, then remove. The custard is done when a toothpick to the center exits clean. Allow to rest 15 minutes before edging with a thin knife and turning out onto a plate. Sprinkle with the toasted bread crumbs and remaining 1/4 cup grated cheese before serving warm.