For the sausage and apples maple agrodolce: Put 1 tablespoon of the canola oil in a cast-iron skillet over medium-high heat. Add the sausage and cook, stirring occasionally, until deeply browned, 8 to 10 minutes. Set aside.
Put the remaining tablespoon of oil in a medium nonstick skillet over medium heat. Add the onions and toss to coat with the oil, then add the apples, 2 tablespoons of maple syrup and some salt and pepper and cook, stirring frequently, until the apples and onions are very soft and caramelized, about 10 minutes. Add 1 tablespoon of the apple cider vinegar and remove the skillet from the heat. Stir the sausage, thyme and parsley into the caramelized apples; transfer to a bowl and keep warm.
Put the nonstick skillet back over low heat, add the remaining 6 tablespoons maple syrup and 3 tablespoons cider vinegar and swirl a few times to make the agrodolce.
For the Cheddar-black pepper waffles: Fit a baking sheet with a baking rack, put the baking sheet in the oven and preheat the oven to 200 degrees F.
Whisk together the flour, Cheddar, baking powder, sugar, baking soda, salt and pepper in a large bowl. Whisk together the buttermilk, melted butter, hot sauce and eggs in a medium bowl. Add the wet ingredients to the dry ingredients and whisk until just combined. Lumps are ok.
Preheat the waffle maker according to the manufacturer's instructions. Brush the grates with some melted butter. Ladle about 1/3 cup of the waffle batter into each grate, close the cover and cook until golden brown and crispy, about 4 minutes. The waffles will be misshapen, not perfectly square, with rounded corners. When they are cooked, transfer them to the baking rack and continue with the rest of the batter.
To serve, put 2 waffles on each of 4 plates. Top each with some sausage and apples and a drizzle of the warm maple syrup and cider vinegar agrodolce. Serve immediately.