Preheat your oven to 425 degrees. Line a rimmed baking sheet with foil.
Hollow out the round zucchini, reserving about ½ of the flesh. Coat the hollow zucchini with oil, some salt and pepper. Place in the oven for 15 minutes.
While the zucchini is baking, cook the sausage in a large skillet. Set aside when cooked through and browned. Using the rendered fat from the sausage, add the onions, reserved zucchini flesh and a pinch of salt to the hot skillet. Cook the mixture over high heat for 4-5 minutes. When the liquid in the pan cooks off, add in the shallots and cook for another 3 minutes.
Reduce the heat to medium, add in the garlic and cook for another 2-3 minutes. Taste and adjust the seasoning. Remove from the heat and mix in the cooked sausage, fresh tarragon and parmesan.
Scoop the mixture into the zucchini shells, filling about ¾ of the way for each zucchini.
Evenly pour the beaten eggs over all of the stuffed zucchini.
Fill the zucchini with the remaining sausage mixture to the top and place in the oven for 30 minutes.
Check for doneness with a small spoon. If the eggs are not set, continue to cook for another 15 minutes.
Once the eggs are set, remove from the oven, top with more parmesan and enjoy hot. Happy eating!