Heat olive oil in a large, oven-safe pot (like a Dutch oven) over medium heat. Add onion, carrot and celery and cook, stirring occasionally, until softened, about 5 minutes. Add the garlic and red pepper flakes, if using and cook, stirring, another 30-45 seconds. Add the diced tomatoes, kidney beans, chicken broth and Parmesan rind, if using. Stir well to combine.
Bring soup to a boil, then reduce heat to medium low and simmer until the carrots and celery are tender, about 30 minutes (taste test to be sure vegetables are tender).
While soup is simmering, prepare the infused oil. Combine the olive oil, sliced garlic and red pepper flakes, if using in a 1 cup measuring cup. Heat lightly in the microwave for just 15-20 seconds, just to release the flavour from the garlic a bit. Set aside. (Alternately warm olive oil lightly in a small saucepan).
Cut the ends from the loaf of bread, cutting about 1 1/2 inches in. Tear into chunks and set aside. Cut 6-8 thick (1-inch-ish) slices from the middle of the loaf and set aside.
Preheat oven to 450F when soup is nearing ready.
When vegetables are tender in the soup, taste and add a generous sprinkling of salt and some freshly ground pepper. Add the kale to the soup in two additions, stirring into the soup as they wilt. Add the bread chunks to the soup and stir to combine. Simmer a few more minutes, then top soup with thick bread slices, covering the entire top of the pot. *Overlap the bread slices slightly for more crispy bread, or lay flat onto the top of the soup for less crispy bread. Drizzle bread slices with several tablespoons of the infused olive oil (don't use it all as you will want to save some for serving). Sprinkle with some freshly grated Parmesan cheese and season with salt and freshly ground pepper.
Place pot into preheated oven (uncovered) and cook for 13-15 minutes, or until bread is toasted and golden around the edges.
To serve, spoon into bowls with soup and a bread slice per serving. Drizzle with additional infused oil and top with additional Parmesan cheese.
Be sure to read the “Ingredient and Cook's Notes" (above the recipe card!), where I share more detailedtips, variations and substitution suggestions for this recipe!