Sear the lamb – In a large pan over medium-high heat, heat olive oil or lamb fat and sear the lamb until browned on all sides. Remove and set aside.
Make the sauce – In the same pan, reduce heat to medium. Add the flour and mix with the remaining drippings, stirring continuously. Slowly add water, whisking until a smooth sauce forms.
Assemble the stew – Transfer the lamb and sauce into a slow cooker (or a pot for stovetop cooking). Add the parsnips, garlic, coriander, cumin, black pepper, and salt. Pour in the remaining water, ensuring the ingredients are submerged.
Slow cook for 6+ hours – Cover and cook on low heat for 6-8 hours, until the lamb is tender and the broth has deepened in flavor.
Add fresh mint – In the last 30 minutes of cooking, add the fresh mint leaves and stir gently.
Serve & enjoy – Spoon the stew into bowls and experience the flavors of ancient Babylon!