DD loves this - its my "go to" if I need 15 minutes peace while I make dinner. I keep meaning to make it a little better by dying the rice but never seem to find the time - she seems quite happy with this version anyway!
Just fill a muffin tin with different types of rice and pasta - I just use whatever I have in the cupboard at the time - leaving 2/3 spaces empty (she had already started moving things around by the time I took this shot!). I give DD a couple of spoons and she happily scoops, pours and mixes until her heart is content.
It's a little messy - the rice usually ends up on the floor - but easy to hoover up.