Heat oil in a pressure cooker and saute onion. Once it starts becoming brown add crushed ginger & garlic, green chilli and curry leaves. Stir for 2-3 minutes. Add masala powders and stir for 5 minutes. when the oil starts separating add beef & potato. Combine well. Add medium thick coconut milk. Bring it to boil. Cover the cooker and put the whistle on. After the first whistle, reduce the flame to low-medium and cook for 10-12 whistles, till the beef & potato is done. Keep the cooker closed till pressure drops, 10-15 mins.
Open the cooker and stir the curry. Check for the doneness of beef. If it's not cooked, pressure again. Once the beef is cooked and gravy becomes thick , add thick coconut milk & mix. When it starts boiling, remove from gas.
Heat oil in a pan & splutter mustard seeds and fennel seeds. Add small onion & curry leaves, once the onion becomes golden brown add it to the curry. This curry is a perfect side dish for chappathi, appam, rice.
Notes
I use Indian Beef for this recipe. The cooking time may vary depending on the type of beef you use.The curry tends to thicken as it rests.