How to Make It
Warm oil in a large skillet over medium-high heat. When oil is hot, brown sausages on all sides, about 6 minutes total. Transfer to slow cooker.
Add onion and garlic to skillet and stir until onion has softened, 2 to 3 minutes. If skillet is very dry, add a tablespoon or two of water. Sprinkle eggplants with 1 tsp. salt and add to skillet. Cook, stirring occasionally, until lightly browned, about 5 minutes. Stir in tomatoes and juice, scraping up brown bits on skillet, and transfer to cooker on top of sausages.
Cover and cook on low for 6 hours or on high for 4 hours. Season with salt, stir in basil and serve.