How to Make It
Heat vegan butter and oil in a large skillet over medium-high. Process mushrooms in a food processor until chopped; add to skillet. Process carrots, celery, and onion in food processor until chopped; add to skillet. Add salt and pepper to taste. Cook, stirring often, until vegetables are tender, about 20 minutes.
Add garlic, fennel, and crushed red pepper; cook, stirring often, until fragrant, about 2 minutes.
Add tomatoes, tomato paste, basil, and another pinch of salt and pepper. Cook, stirring occasionally, until thickened to desired consistency, 20 to 25 minutes. Serve over cooked pasta.