Start by preheating your oven and tossing the eggplant cubes with olive oil, salt, and pepper. Spread them evenly on a baking tray so they roast instead of steam. Roast until they are golden and soft, which gives the sauce its creamy base.
While the eggplant is roasting, bring a large pot of salted water to a boil. Cook your pasta according to package instructions until al dente. Reserve a cup of pasta water before draining, as it helps adjust the sauce later.
In a pan, gently sauté garlic in olive oil until fragrant but not browned. This step builds the aromatic foundation of the sauce. Be careful not to burn the garlic, as it can turn bitter quickly.
Add roasted eggplant, walnuts, plant milk, nutritional yeast, and lemon juice to a blender. Blend until smooth and creamy, adding a bit of reserved pasta water if needed. The texture should be silky and pourable.
Transfer the sauce to a pan and gently heat it through. Add the cooked pasta and toss well so every piece is coated. Adjust seasoning with salt, pepper, and chili flakes if desired.
Once everything is well combined, remove from heat and garnish with fresh parsley. Serve immediately while warm and creamy. The flavors deepen as it sits, making it even more delicious.