Baking concentrate using Hard Alcohol ex Jack Daniels

You can't. The compounds which make Jack Daniels taste like Jack Daniels are alcohol soluble and highly volatile. If you try cooking off the alcohol, the taste will evaporate together with the alcohol.

If you are thinking of "rum essence" for baking, that's not derived from rum at all. It's simply ethylformate, and it's produced in a lab.

You can mix xanthan gum or something else with alcohol, but it won't make it a concentrate in any way. In fact, it is likely to make the taste somewhat weaker, as these thickeners have a tendency of trapping taste.

This is just an idea. I have used it in the past and had to put it here as it may help out aficionados like you!

Using a meat injector, with a fine needle, you can make an alcohol syrup. I use Hershey's light and dark syrups. Mix one part hard liquor to three parts syrup and inject it into your cake just after baking. Do not remove the cake from the oven yet; leave it there to soak for five minutes so it uses the residual heat to help the moisture dissipate evenly into the cake. Make sure you do not add too much into one area as it will make your cake a little soggy inside (unless you like it that way).

One other tip is to keep the alcohol syrup in a hot water bath at about 50°C / 120°F. This way it does not shock your bake and penetrates better (while not being so hot that it causes the alcohol to evaporate).

Good luck!

I've made some quite successful (given the rate they disappeared) gin & tonic cupcakes. I concentrated the gin but also reinforced the flavour.

I didn't document the process in quite enough detail to give a full recipe but I started with an orange cupcake recipe that used juice in the mixture. In place of the juice I used a reduction of gin, infused with added juniper berries and lime zest as it simmered*, strained (then diluted with tonic water and lime juice)**. The icing was a slightly wet buttercream with reduced tonic and lime as the liquid.

So the process will be far easier with spirits that have a dominant flavour that you can reinforce, as some will be lost to the reduction. In many cases you'd be talking about caramel and possibly vanilla, though some oak chips would make for an interesting experiment (possibly infuse for longer before reducing).

If you were starting with fortified wine or low-proof spirits and wanted to maintain the alcohol (or didn't mind), freeze-distilling would preserve volatile, alcohol-soluble flavourings. This wouldn't work over about 30% unless you have access to something colder than a normal freezer (dry ice, or perhaps trickery with freezing point depression using ice+calcium chloride - the more usual ice+table salt approach wouldn't go cold enough)

* Infusion, decoction, or something in between?

** Knowing that alcohol doesn't all boil off, especially in baking, I still wanted low alcohol, which is why I reduce the gin then added the tonic, rather than reducing/infusing the mixed G&T.