Heat 1 tablespoon of the oil in a large skillet over medium heat. Add the mushrooms. Cook for 7-10 minutes, or until the mushrooms have released their juices and are tender and reduced in size, stirring frequently.
Add the remaining teaspoon of olive oil, then add the tomatoes. Allow the tomatoes to cook in the pan for 3-4 minutes without stirring them (this will help them to brown gently and start to burst). Add the garlic and vinegar. Continue to cook everything, stirring every now and then, for a few minutes, or until the tomatoes are soupy and tender. Stir in the lentils and the vegan bacon or sausage, if using. Mix everything well and cook for another 2 minutes, or until the mixture is warmed through. Taste and add salt and freshly ground pepper as needed.
Remove the mixture from heat. Serve over baby arugula, with an extra drizzle of balsamic if you like. You can also make it ahead of time, refrigerate it, and reheat or serve cold later. Enjoy.