Line a plate with paper towels. Heat vegetable oil in a wok or large saucepan over high heat. Add eggplant; cook and stir until softened, 2 to 3 minutes. Remove eggplant from wok; drain on paper towels.
Combine onions and garlic in the same pan. Add red bell peppers; cook and stir for 3 minutes. Season with curry powder. Pour in coconut milk and season with salt and pepper. Bring to a simmer and add eggplant. Increase heat to high and bring to a boil. Cook, stirring constantly, until flavors are combined, about 3 minutes. Sprinkle with mint.