- In a 3 1/2-quart Dutch oven over medium heat, warm 2 tablespoons of the olive oil. Add the pancetta and cook, stirring occasionally, until crispy, about 5 minutes. Add the onion, carrot and celery and cook, stirring occasionally, until beginning to soften, about 8 minutes. Add the garlic and cook for 1 minute. Add the cannellini beans, broth and thyme and bring to a simmer. Reduce the heat to low, cover and cook until the vegetables are tender, about 10 minutes.
- Remove the pan from the heat. Using an immersion blender, puree the soup until smooth. Stir in the cheese and season with salt and black pepper. Keep the soup warm.
- Meanwhile, brush the baguette slices on both sides with olive oil and season lightly with salt. Heat a cast-iron grill pan over medium-high heat. Toast the bread, turning once, until nicely grill-marked, about 2 minutes per side. Set aside.
- In the blending cup of an immersion blender, chop the roasted red bell peppers. Stir in 1/2 teaspoon salt, the remaining 2 tablespoons olive oil, the parsley, vinegar, red pepper flakes, honey and black pepper. Top the baguette slices with the roasted red bell pepper tapenade, dividing evenly. Ladle the soup into warmed bowls and serve immediately with the crostini.