Heat oil in a large heavy-bottomed pot over medium-high heat. Brown lamb pieces well on all sides, working in batches if necessary. Remove and set aside.
In the same pot, sauté onions in oil for 5 minutes until softened. Add garlic and ginger, cook for 1 minute until fragrant.
Stir in 3 tsp Goan spice blend and 1 tsp sweet spice mix with a splash of water. Cook for 1 minute.
Add chopped tomatoes and stock, return lamb to pot. Bring to a simmer, cover and cook for 1 hour until lamb is tender.
Add spinach and chickpeas to the pot, cooking until spinach wilts. Stir in remaining spices (2 tsp Goan, ½ tsp sweet spice), cook 5-10 minutes.
Remove from heat and cool slightly. Mix in yoghurt, lemon zest, chopped parsley, salt, and pepper to taste.