I have never used stevia, but your post got me curious: here's link to drying and making stevia powder.Curious have any of you replaced sugar with real stevia? I've got a plant growing happily but I'm not really sure what to do with it. All the talk about custard made me think that might be a good place to start...I could add a couple of leaves to the milk when heating maybe?
http://www.gardenguides.com/116522-use-stevia-plant.html
There's not a lot of info about using green leaves except you can place them in a warm beverages and get some earthy sweetness - not sure how that would taste in custard.