In a large pot or dutch oven, add the chopped bacon to a cold pan. Turn the heat to low and slowly render the bacon, stirring occasionally, until crispy. Using a slotted spoon, transfer the crispy bacon to a plate lined with paper towels and set aside. Reserve 1 tablespoon of bacon fat for the croutons and discard (or save) the excess, while leaving 2 tablespoons of fat in the pot.

Add the thinly sliced onions and fennel to the pot and increase the heat to medium. Cook, stirring constantly until the onions and fennel are very soft and translucent. Add the minced garlic and sugar and cook for another 5 minutes or so.

Increase the heat slightly and add the tomato paste, fennel seed, and Calabrian chilies, and cook for 1 minute. Add the white wine to the pot and stir to bring up any browned bits from the bottom of the pot and simmer for 2 minutes. Add the crushed tomatoes and broth and bring to a simmer for about 15 minutes, until slightly reduced. Turn off the heat and add the cream and basil leaves.

Using an immersion blender or standard blender (you may have to do this in batches), blend the soup until smooth. Return to the pot and season to taste with salt and pepper. Serve topped with herby croutons (below), a drizzle of olive oil, parmesan cheese, and topped with the crispy bacon bits.

Make the croutons: Preheat an oven to 400 degrees F and line a baking sheet with parchment paper. In a large bowl, toss the cubed bread with the bacon fat, olive oil, basil, parmesan, crushed red pepper flakes, and salt. Spread out evenly on the baking sheet and bake for about 7-9 minutes, until slightly golden brown. Remove from the oven and cool slightly.