In a frying pan melt butter over medium heat. Add mushrooms and cook for 10-15 minutes, until golden brown. In a separate pan over medium heat, sautée diced tomatoes with oil and Italian seasonings. Cook for 10 minutes.
Spread mashed avocado on each toast. Top with sautéed tomato mixture and mushrooms. Sprinkle with sesame seeds and serve with fresh basil leaves. Enjoy.