Juicy, tart mangoes are surprisingly excellent at cutting through the richness of the avocado in this open-faced sandwich. Unfortunately, it can be hard to predict just how sweet they’ll be. If you’re working with an especially ripe or fruity mango, make sure to compensate with additional lemon juice to keep the sweetness in check. A sprinkle of chili powder adds contrasting heat that more firmly anchors this toast in savory territory. Chopped mint delivers an aromatic, herbal touch, but basil would do nicely here as well.