Ericha kozhambu (kozhambu that is heated again & again) also called as "ezhu kari kozhambu" or "Thalagam" is simply arachu vitta kozhambu (spicy lentil gravy) made with seven vegetables. My mom makes this kozhambu during two occasions - Thiruvathirai & Pongal. Although the name suggests to add 7 vegetables, you can add more (or) less vegetables as you want. But, it is a practice to add odd number of vegetables (though I don't know why). Usually vegetables like potatoes, sweet potatoes, yams, winter melons, butternut squash, raw banana, broad beans etc are used. Traditionally, "only Tamil vegetables are used in this kozhambu". Carrots, radish etc are supposed to be English vegetables and hence not used in this kozhambu. Vegetables that tends to get mushy are also not used. Having said this, feel free to experiment it with veggies of your choice.
I am a great fan of this kozhambu and I love it especially on the second (or) third day and it tastes unbelievable with dosa (or) as a side for curd rice. For those who don't know, this kozhambu is made in excess and will be reheated and used for 2-3 days.
Margazhi Thiruvathirai is basically Lord Shiva 's birthday and I always used to wonder why kali & kozhambu is offered to Him as Neivedhyam. Recently, I read an interesting explanation for it at subbuskitchen and I thought it was very convincing.
Sambar powder - 1 tbsp
Tamarind - 50 gems or 1 small lemon size
Cooked & mashed toor dal - 1 cup
Oil & Salt - to taste
Mustard seeds - 1/4 tsp
Curry leaves - Few
Roast & grind
Hing - small piece
Fenugreek seeds - 1/2 tsp
Red chillies - 4 nos
Red chillies - 4 nos
Coriander seeds - 1.5 tbsp
Grated coconut - 2 tbsp
Roast all of the ingredients (under 'Roast & grind') except coconut in a pan with little oil and grind it along with the fresh coconut. Taste of the kozhambu changes, if the coconut is also roasted. Mix the ground masala & cooked dal into a paste with little water. Take care not to add too much of water, as consistency of the kozhambu will be very watery.
Heat oil in a pan/vessel. Add mustard seeds and let it splutter.
Add tamarind water followed by vegetables, sambar powder, salt and allow it to boil until the raw smell of tamarind goes and the vegetables are cooked. Now, add the ground paste + dal mixture to the kozhambu and bring it to a boil.
Garnish it with curry leaves and enjoy with kali.