Preheat oven to 425 F.
Preheat a large nonstick skillet on medium-low heat along with the oil. Once hot, add in the onion slices and cook, stirring rarely until they start to turn amber brown, about 45 minutes.
Add in the maple syrup and apple butter and season with salt and pepper. Cook for another 5 minutes or so until the sugar was melted and any new water from the onions has evaporated. Set aside.
Roll each sheet of puff pastry to about 1/8 inch thick. Slice the puff pastry into 5 rows by 3 columns to make 5 pieces. Set aside.
Slice through the casing of the sausages, cut each sausage in half. Remove each half from the casing.
Working one at a time, lay down about a teaspoon of the caramelized onion/ apple butter mixture onto one of the puff pastry pieces.
Take one half of a sausage, and roll it in your hands with about 1/2 teaspoon of breadcrumbs. Roll back into a mini-sausage shape, and lay it on top of the caramelized onions. Roll the puff pastry around the filling and tuck in the ends. Place the sausage roll on a baking sheet lined with parchment paper.
Continue with the remaining sausage rolls, positioning them 1 inch apart (this may require a few batches or extra baking sheets).
Mix together the crushed pecan crumbs, brown sugar and maple sugar.
Brush the tops of the sausage rolls with melted butter and sprinkle with the nut topping. Bake for about 25 minutes, or until the pastry is golden brown on the top and bottom.