Heat oil in a Dutch oven or small stockpot over medium heat. Add pancetta and cook, stirring often, until pancetta is lightly browned around the edges and fat is partially rendered, about 5 minutes. Add onion, carrot, celery, and potato and season with salt and pepper. Cook, stirring often, until vegetables are softened and onion is translucent, 10–12 minutes. Add garlic and cook, stirring, until fragrant, about 2 minutes. Add tomatoes, lightly breaking them up with your hands as you add to the pot; add chicken broth, bay leaf, and Parmesan rind. Bring to a simmer, season with salt and pepper, and add kale. Simmer until potatoes and kale are tender, 10–15 minutes. Remove from heat and add pasta, rice, and/or grains. Serve with basil, grated Parmesan, and a drizzle of olive oil.