These elegant crostini are sure to impress guests at any party. Also try:Eggplant Caponata Crostini, Crostini with Fresh Ricotta and Grilled Radicchio
Heat olive oil in a small saucepan over medium heat. Add garlic, rosemary, sage, red-pepper flakes, and 1/2 teaspoon salt; season with pepper. Cook, stirring, until garlic is soft and golden, 6 to 8 minutes. Add cannellini beans and cook until heated through, about 3 minutes.
Transfer bean mixture to the bowl of a food processor. Add red-wine vinegar and process until smooth. Season with salt and pepper and set aside.
Preheat a grill pan over medium-high heat. Brush bread on both sides with olive oil. Place bread slices on grill pan; cook, turning once, until bread is toasted and grill marks appear, about 2 minutes per side.
Spread two tablespoons white bean puree on each slice of grilled bread. Top with tuna and sliced olives. Sprinkle with parsley and serve.