Great minds are obviously thinking alike here coz I've been doing this over the last few weeks to try and get it right, for me. I'd pretty much go with all that DD says but try using 50/50 mix of split red lentils and washed moong dahl, they both cook in around 25 mins and you get the smoothness of the red lentils with added texture of the moong dahl, loverly. Also try sizzling a tsp of yellow mustard seeds in the ghee/oil before adding the lentils, gives the finished dahl an extra depth of flavour.
Regards
CoR