In a big bowl mix Rice Flour with salt and butter.
Grind green chillies, ginger, curry leaves and cumin seeds to a coarse paste in blender.
Add ground paste to the flour and mix well.
Add drained chana dal and sago and mix well.
Just sprinkle few drops of water (1/4 cup approximately) and knead to a smooth dough.
While you start making the chakkalu, heat oil over medium heat in a deep pan or kadai.
Divide the dough into equal gooseberry sized balls.
Smear few drops of oil on a plastic sheet or a butter paper. Take each ball and flatten it using your palms to a disc, 2-3" in diameter on the greased sheet.
Repeat the process and make around 6 to 8 for each batch depending on the size of your kadai.
Once the oil is smoking hot, slide them carefully into the kadai.
Fry them over medium heat until golden brown turning sides in between for even browning.
Once they get the light golden brown colour, drain them onto an absorbent paper napkin to remove excess oil.
Repeat the process till you are done with the dough.
Cool down completely and store them in an airtight container.