In a deep pan or a kadai, add oil. Keep the flame in medium, Once the oil is hot, add mustard seeds and allow it to splutter fully. Next add in the fenugreek seeds and white urad dal and sauté for few seconds. (be careful not to let the fenugreek seeds burn. If it does it will give a bitter taste to the gravy) Next add in the shallots and garlic pods, sauté until the onions are slightly cooked (don't have to brown the onions). Next add in the chopped tomatoes and mix it in well.
cover it with a lid and cook for 5 mins until the tomatoes are cooked and turns soft and mushy.
Add the kuzhambu milagai podi or sambar powder and mix it in well.
Add the extracted Tamarind pulp and about 2.5 cups of water. (This curry thickens as it boils so keep it a little thin at this stage)
Add grated jaggery to the gravy, salt and cover it and cook in medium to low flame for 10-15 mins. And continue to cook on medium flame for 10 mins with out the lid.
When the gravy is ready you can see that the gravy has thickened, the onions have turned translucent and oil has started to appear on the sides. This is the sign that the gravy is ready.
And there chinna vengayam poondu kuzhambu is ready to serve. Enjoy it with hot steaming rice with appalam