This dish is one that appears at most Colcannon Christmas feasts. I don’t eat a lot of red meat but when I do I like lamb. Luckily I live not too far from a good number of Middle Eastern markets where halal lamb is to be had at very reasonable prices. Rather than get the ‘prettier’ cuts from leg or shoulder I buy the lamb that’s already chopped for stew. This has bone and fat still still mixed in but makes for a richer, tastier dish, in my opinion.
I like to cook the dish covered for a good long time and then reduce the sauce. I also think that leaving it to rest for a day improves the flavor.

1/2 cup vegetable oil
3 - 4 lbs lamb cut into cubes
3 oz fresh ginger, peeled and chopped
10 cloves garlic crushed and coarsely chopped
1 large sweet onion finely chopped

Whole spices:
12 black peppercorns
12 cardamom pods (white or green)
8 cloves
1 large bay leaf

Ground spices:
3 tsps ground cumin
2 tsps ground coriander
1/4 tsps ground cinnamon
6 teaspoons Hungarian paprika
cayenne to taste - a teaspoon is about right.
salt to taste - about a teaspoon.

Have your whole spices and ground spices ready for use.
Make a paste of the ginger and garlic. You’ll need to use some water if you’re using a blender.
Brown the lamb in batches in the oil and set aside
Add more oil if needed, then add the whole spices. Stir once then add the onions.
Sautée the onions in the oil. If you keep the heat high and keep them moving so they don’t burn, then 5 minutes should be enough.
Lower the heat and add the ground spices and sautée for a minute or two.
Now add the ginger/garlic paste, mix in well and cook for about a minute. 
Add a cup of water and deglaze any bits stuck to the bottom of the pot.
Return the browned lamb to the pot.
Add water until the meat is submerged and stir in a teaspoon or so of salt.
Cover and cook on low heat for two or more hours.
Remove the lid and cook another hour on very low heat until the sauce becomes thick.
Serve on plain basmati rice with some raita on the side.

Note: The underlying structure of this dish can be applied to many others. The sautéd onions and ginger/garlic paste are a common base in many dishes. The whole spice can also be whole cumin seeds, whole coriander seeds, mustard seeds, red pepper flakes -- whatever you think will make the dish the way you want it. Then adding the ground spice -- ground cumin and coriander are common. You might also add ground fenugreek and/or turmeric for instance.