Heat oil in a medium frying pan over medium heat. Peel and core ½ pear, then cut into small dice. Combine diced pear with onion and celery and season with salt and freshly ground black pepper. When oil shimmers, add pear mixture to the frying pan and sauté until onion is translucent, about 5 minutes. Add garlic and cook until just soft, about 1 minute more.

Remove pear mixture from heat and transfer to a medium bowl. Allow mixture to cool in the refrigerator for about 15 minutes.
Remove sausage from its casing. Crumble sausage into cooled pear mixture. Add egg, breadcrumbs, milk, cinnamon, and paprika. Mix well. (To ensure mixture is properly seasoned, form a small patty and sauté it in a pan over medium heat until browned and cooked through, about 2 minutes per side. Taste and adjust seasoning. Repeat if necessary.)

Heat the oven to 350°F and arrange a rack in the middle. Cut remaining 6 pears in half lengthwise and remove the stems. Cut off a small slice from the uncut side of each pear to create a flat base for the pear to rest on while roasting. Using a melon baller or a small spoon, scoop out the core and another ½ inch or so around the core to create a hole for the sausage mixture. Season each pear with salt and freshly ground black pepper.

Divide sausage mixture among pears, filling each half generously. Place stuffed pears in a baking dish. Bake until pears are soft and stuffing is browned on top and cooked through, about 35 minutes.