Make the ragu: Put the garlic, celery, onions and fennel in a food processor and puree to make a coarse paste. Coat a wide, deep pan with the olive oil and put over medium-high heat. Add the pureed veggies and season with salt; cook until all the liquid has evaporated and the veggies begin to stick to the pan-you want to brown the crap out of these guys until crud starts to form on the bottom of the pan. Stir occasionally to scrape up the browned bits, then let the crud form again. Be patient here and don't rush it: This is where the big flavor develops; it will take up to 30 minutes.
When the lovely brown crud has formed and been scraped down a couple of times, stir in the tomato paste. Let it start to brown a little, stirring, 2 to 3 minutes. There's not much liquid at this point to keep things from burning, so move fast: Add the wine, stir to combine and scrape up any remaining browned bits. Cook until about half of the wine has evaporated, 4 to 5 minutes.
Add the sausage and cook, breaking it up with a wooden spoon, until browned, 10 to 15 minutes. (This is where another round of big flavor is formed, so take your time.)
Add enough water to cover the meat by about 1/2 inch. Stir to combine well, then add the bay leaves and thyme bundle. Taste, season with salt and taste again; it's by no means done, but it should taste good. Bring the sauce to a boil (BTB) and reduce to a simmer (RTS). Continue cooking for 3 hours, tasting, seasoning and adding more water as needed. Discard the bay leaves and thyme.
Meanwhile, make the pickled onions: Combine the vinegar, 1/2 cup cold water, the sugar, 1 tablespoon salt and the hot sauce in a bowl. Add the sliced onion and let sit, at least 1 hour. Drain.
Assemble the nachos: Preheat the oven to 350 degrees F. Spread a layer of tortilla chips on an ovenproof platter. Top with a layer of the ragu and cover with the parmigiano and fontina cheeses. Bake until the cheeses melt, 5 to 10 minutes. Meanwhile, mix the chopped chipotle, adobo sauce and mascarpone in a bowl. Sprinkle the arugula over the nachos and finish with dollops of the chipotle mascarpone and the pickled onions. A gooey cheesy treat. Delish.
Photograph by Con Poulos
Recipe courtesy Anne Burrell for Food Network Magazine