1 T of natural peanut butter
2 T of sugar free fat free cheesecake instant pudding mix
1 cup unsweetened almond milk
handful of ice
mix in the blender

I bet you could play with this some with the flavor of pudding mix. I've got ideas.
And not too many calories. You could even use skim milk if that would be more to your liking and plan to making it lower fat.