Preheat your oven to 325°F (163°C).
Heat olive oil in a large ovenproof pot over medium-high heat.
Sear the lamb shoulder on all sides until browned.
Remove the lamb from the pot and set aside.
Add diced onions, carrots, and celery to the pot, and sauté until softened.
Stir in minced garlic and cook for an additional minute.
Pour in the broth and stir, scraping up any browned bits from the bottom.
Return the lamb to the pot, along with rosemary, thyme, salt, and pepper.
Bring the mixture to a simmer, then cover and transfer to the oven.
Cook in the oven for 3 to 4 hours, or until tender.
Once done, remove from the oven and let the lamb rest for 15 minutes.
Serve with the vegetables and sauce from the pot.
