This Indian restaurant spice mix is one of the key tricks restaurants use to make their curries.
Mild curry powder can be any commercially available curry powder. I personally like Boltz for this recipe but there are many out there.
Chili powder is Indian chili powder. It comes in different heat levels, from mellow to blistering hot. You want mild for this recipe. Look for kashmiri mild chili powder at any Indian grocery store. The flavour is quite distinctive. In a pinch, you can use something like New Mexican Red chili powder.