Heat the vegetable oil in a large pot over medium heat. Once the oil is hot, add the onion, carrot, celery, and capsicum, sautéing until they become tender and translucent. Add the minced garlic and continue to sauté until fragrant.
Add the pulled lamb into the pot, stirring to combine with the vegetables. After a couple of minutes, add the chopped tomatoes, tomato paste, and water. Stir in the chopped parsley, sage, and rosemary. Reduce the heat to low and let the mixture simmer for an hour, allowing the flavours to meld together.
While the ragu is simmering, prepare the pappardelle pasta. Bring a large pot of salted water to a boil. Add the pasta and cook according to the package instructions until al dente, which is cooked through but still has a slight bite. Drain the pasta, reserving a cup of pasta water.
Add the drained pappardelle pasta to the simmering ragu, stirring well to ensure the pasta is evenly coated with the sauce. If the sauce seems too thick, add a bit of the reserved pasta water to loosen it. Stir in the spinach leaves. To serve, scoop portions onto plates and top each with a spoonful of ricotta cheese and a sprinkle of grated parmesan cheese and chilli flakes. Enjoy your hearty lamb ragu with pappardelle pasta.