I had an idea for halloween, which involves baking a sponge cake and piping icing on it to make it look like a brain. For bit more authenticity, I was hoping to get some red jam or something to vein the cake.
After a bit more thinking about it, to get proper veins, I'd need something like strawberry bootlaces.
I wouldn't bake them in, for a start, as I wouldn't be confident of what the bootlaces would do in the oven. Thinking about it, a possible way of going about it is to 'thread' the bootlaces through the cake before you ice it.
Cut the cake in half (vertically), get a big needle like a darning needle or something similar, and (carefully) thread a few laces through, cutting them off flush with the surface, then stick the cake back together with icing or jam and pipe on the outer icing. The tricky thing will be getting them to follow curvy paths.
The other thing you could do is use said needle (or perhaps a chopstick) to poke little tunnels through the cake, then pipe red jam into them. This would perhaps give a nicer result - it might be a bit odd to be eating a slice of cake and then to suddenly be chewing a rubbery bootlace.
You can try cooking a cake with jam/jelly already in it, so that the stuff will ooze in appropriate places. That will work better on a sponge mix that is short on flour, so it becomes a pudding. You could serve that with green colored "custard".
Nothing looks more like a brain than a cauliflower cooked without cutting! That could be "decorated" with cranberry sauce and served with "MEAT" - don't tell 'em what the meat is!
Do the "veins" have to be liquid? Why not use red food coloring on a small reserved portion of your batter, then swirl some of the retained batter as you would with a marbled pound cake?
I can't say I've done exactly what you're trying to do, but I've had quite a few attempts at setting gummi laces into jello, and I really don't think it's going to work to bake them in.
You have a few major problems:
Gummi laces do strange things when they get wet. They swell up to about 2-3x their size (in every dimension ... so 8-27x volume), diluting the flavors and make for a really nasty texture.
Gummi laces melt when they get warm. (exact temperature depends on the concentration of gelatin ... but setting them in a wet batter means the gelatin will dilute ... I'd expect them to melt well before the cake sets).
Gummi laces really don't like to hold their shape. Especially when wet or heated, they'll attempt to go back to whatever shape they were originally made as. (I had tried using these red coil ones which were thicker ... caused other problems).
So, some suggestions, first to get the brain look to the cake:
update (and deletion re: setting the laces under the frosting):
For the arteries on the brain (note, arteries are red, veins are blue), you'll need something to afix the laces onto the cake. You'd likely best off using something to 'glue' to the laces onto the cake that isn't too wet ... unfortunately, I'm not really sure what that is. Typical food-safe glues are royal icing, egg whites, or a dab of corn syrup. Unfortunately, all of these have a lot of moisture, are might cause your veins to deform (as they absorb the moisture).
I honestly don't know what the best solution for that would be.
If you were to use a buttercream frosting for the cake, you'd have issues with losing the creases of the brain, but you might be able to set the laces into the frosting before it's hardened. For this, I would pre-cut bits of the lace so that you can both work quickly and not have to worry as much if the laces decided to start changing shape on you.
