Welcome to PF, Selseg.
You should be able to use the 'lost-wax' process that most bronze foundaries have, but on a smaller scale.
Carve the medal as you want it out of wax.
Poke a small hole in the bottom of a tin can, with a slender piece of stiff material such as piano wire stuck through it to an inch or so.
Pack wet sand around the wire to just even with the top of it.
Place your wax model on top of the sand, just touching the wire.
Pack more wet sand around firmly around and over the model, with another piece of wire in contact with the top of the model and sticking up past the top sand.
Hold the can solidly with a set of tongs or pliers, pull out the bottom wire, and heat the can with a torch. The wax will melt and run out the bottom hole, leaving an exact imprint of the model in the sand cavity.
Stick the bottom wire back into place and pull out the top one.
Pour your molten metal into the top hole and leave the whole thing to cool.
Once it's set, dump the whole works out and collect your medal. There'll be tiny imperfections called 'sprues' where the wires were, much like those on a plastic model part when it's removed from the 'tree'. Touch them up with something like a Dremel or a small file and a buffing wheel, and you're done.
Since I don't know your age, I will assume the worst and encourage you to be extremely careful when dealing with anything that hot, and particularly with an open flame when wax is present.
For an easier and safer, but lower-quality, process, you can make a separate mould for each side (1/2 of full thickness) by sticking your model into plaster of paris. When it's hard, pack JB Weld or other metallic epoxy into the moulds, then bond the two halves together after they're cured.