Hello, and thank you very much in advance for any input/suggestions/help. I am new here (first post!) so your patience is appreciated. 

Some background info I feel might help you help me: I am making my best friend a cake for her bday (10 May) and want to do a HP themed cake, specifically the Doe that is produced when Prof. Snape casts his patronus*. I checked for information I need online-but I fear I may not know the correct terminology to get adequate results, because I found zilch.

END GOAL: I want/need a 3-Dimensional, transparent (clear, with blue-y highlights) doe that stands up on it's own, about 12cm high. And if possible, I want this to have LED lights inside of it, but I think that's a little too far-reaching.

I figure that sugar is the only medium (or Isomalt) I could possibly use to get such an effect -a  solid, transparent and totally edible casting/figurine/sculpture/thingymajiggy(what even do I call it?). Using the pull/blow process wouldn't work - I don't have the skill, knowledge or equipment. But I've seen isomalt jewels, they're a thing - surely other shapes would be possible too, even more intricate ones? So my question really is - is it possible to cast molten sugar into a silicone mold and result in a 3D, free standing, solid, rather small structure? Also, I have to make my own mould! Because here in NZ there aren't a lot of places to buy things that aren't typically common, like candy moulds. So I have bought some food grade silicone, a hard plastic doe figurine, and... That's as far as I'v got. I have no modelling experience (lol) but I like a good challenge.

I'm thinking once I have the silicone, the best way to go would be to make two moulds, seperately, of each half, and just before the sugar gets hard, stick 'em together. They'd have to be perfect though, so, not sure. But pouring sugar through a funnel into a block mould and then cutting it out also seems risky, sugar is a delicate business. Wonder if there are any modelling/casting experts reading who could offer up some advice... And isomalt, or sugar? Probably isomalt. Not sure?

Please help! 

*If you just google image search doe patronus you get lots of hits! I'm not going off any particular picture, because replicating it exactly would be impossible! But I have a good mind image of what I want it to look like :)

first off i'm not a sugar master or anything but i've worked with it  -- if i did your method of putting two halves together -- i would let them set up entirely then probably blow torch them to make them stick together --

but the idea of pouring into a cast mold would be easiest i think -- 

but even if you did a flat two dimensional doe and just stood it up that would be pretty cool too -- you can make a cookie cutter type mold easy peasy -- there are many tutorials online for making cookie cutters (that you could pour hot sugar into) 

and blowing sugar requires no special equipment -- the first time i used an empty bic pen aka cheap hard plastic 'straw'-- just the ink inside part was removed and i used the pen's housing as the straw to blow into -- worked great -- 

sugar often yellows or browns a bit as it cooks -- so you might get a more green effect rather than blue -- isomalt comes out more true to color and doesn't brown as easy -- but isomalt will make peeps sick if they eat too much --

so... that should get you started maybe -- 

Masters probably wasn't the best term to use, sorry about that. Thanks for your advice :) I'm going to attempt a few different ways all using isomalt-I brought a lot of silicone and figured I may as well play around with it. I think you might be right though-2D seems like it might have the best results. And will be so, so much easier. I will post results.

A bic, really? That's creative! I thought you would have needed that special equipment I always scroll past when I see the prices haha. I really want to learn how to work with sugar, both blown and pulled, but classes for it where I live are few and far between (maybe even never!) and my internet connection is so bad it doesn't load videos to learn online easily :( But it's just so wonderful! 

Thanks a lot for your input, much appreciate ^_^ 

When I saw the title of your post I thought you meant actual "cast" sugar which is simply sugar moistened and put in a mold, see Julia Usher on YouTube for her videos, this would give you an opaque sugar doe which is pretty. The other suggestion to get a clear doe could be melted glacier mints. I've only made snowflakes and a small bunny with this but  they stay clear or icy blue and I melted them in the oven over tin foil. The blue glacier mints are very pretty (this was during The Great Frozen Cake revolution of 2015 when every little girl needed an Ice palace for her birthday)

I used 2 bags of glacier mints, melted them slowly in the oven at around 160 degrees (watch like a hawk, they appear to not melt for about 3 mins....then lava!)

I'd use one of those disposable foil pudding basins then you can bend a lip into the basin to allow you to pour into your mold. x