Dry roast it over low heat (on a number scale 2) for about 10 to 12 minutes or until the horse gram turns deep brown/red. As you can see in the step 1 picture, horse gram lentils come in different shades of brown. The light brown ones should turn golden brown, and the darker shade lentils will turn deep brown. Don't let the lentils turn black. As you roast, you will hear the popping sound; you can turn it off at that stage and always roast in medium-low or even low heat. Transfer it to the mixer jar and let it cool.
In the same pan, add ½ tsp oil, and when the oil is hot, add the dried red chilies and urad dal.
Roast until the urad dal turns golden brown. Transfer it to the mixer jar.
In the same pan, add ½ more tsp of oil, and when it is hot, add the chopped garlic cloves and roast until it is soft and turns light brown.
Transfer it to the mixer jar. Allow all the ingredients to cool. Add the coconut, tamarind paste, and salt to the mixer jar and grind it coarsely by adding 3 to 4 tbsp of water. Transfer it to a bowl. If you plan to serve this with idli or dosa, add more water and grind it smooth.
In a separate tempering pan, heat the remaining tsp of oil. When the oil is hot, add the mustard seeds and curry leaves. Let the mustard seeds splutter and curry leaves crisp up. Add this to the ground chutney. Serve it warm with rice or idli/dosa.
The garlic cloves that I used were pretty big, and it was approx 20 grams. You can use up to 25 grams of garlic cloves. Depending upon the size and taste preference, you can adjust the measure.
Adjust the salt and spices to taste.
I used Bydgi variety red chili, and it was mild but gave nice color to the chutney.
I highly recommend gingelly oil, but you can use any neutral oil.
As I served it with chutney, I added only 4 tbsp of water. If you plan to serve with idli or dosa, you can add ½ to ¾ cup to bring it to pouring consistency and grind the chutney smooth.
Along with garlic cloves, you can add one or two shallots for added flavor.