Place eggplant halves, cut sides up, onto a baking sheet and brush with 1 tablespoon olive oil.
Bake eggplant in the preheated oven until soft, 30 to 35 minutes. Peel eggplant when cool enough to handle; set aside.
While eggplant is baking, place potatoes and garlic cloves into a large pot and cover with lightly-salted water. Bring to a boil, reduce heat to medium-low, and simmer until tender, about 20 minutes. Drain.
Place bacon in a large skillet and cook over medium-high heat, turning occasionally, until evenly browned, about 10 minutes. Drain bacon slices on paper towels and retain 1 tablespoon drippings in the skillet. When bacon is cool, crumble, and set aside. Cook and stir onion in bacon drippings until soft and translucent, about 5 minutes. Set onion aside.
Place eggplant, potatoes, cooked garlic cloves, and 1 tablespoon olive oil in a large bowl and mash with a potato masher until smooth and thoroughly combined. Season to taste with salt and cracked black pepper. Serve in a bowl topped with cooked onion and crumbled bacon.