Wash the plain rice very well. Soak in lots of water overnight.
Similarly wash the urad daal and soak along with the fenugreek separately overnight.
Next day morning, in your big jar of any Indian mixer (Prithi, Premier, etc.), drain out the rice and grind it to a thick batter adding very little water, to as smooth as possible. It may be slightly grainy but that's OK. Pour into a large saucepan.
Next, add the drained urad daal along with the fenugreek and grind to a smooth batter adding a little water.
Pour this ground daal mixture into the rice mixture and mix well with hand. You can use a ladle but mixing with hand will speeden up the fermentation process.
Close and keep in a warm place for around 8 hours to ferment.
Once fermented - you can recognize it by a yeasty smell and swollen texture - add salt to taste and mix well.
Keep your idli steamer with water on the stove and grease your cooking plates well. Pour little into each hole and steam for around 10-12 minutes on meduim flame.
Take out the plates, leave to cool slightly before taking out with a spoon into your hotpot. Keep covered till serving.
Serve warm with hot sambaar and chutney! Yum...