How do I make a thicc hot chocolate like the ones you get at a bar?

Sure you can, heavy cream and milk should be pretty good. Ratio dependent on how thick you want it. A good whisk and some effort should get exactly what you want.

cornstarch or xanthan gum

nice dubs

this though. Make a thin ganache. Hot cream over chocolate, whisk adding more cream until desired consistency, like I said here

You can use milk but cream is more rich. You can heat the cream in the microwave. You don't need to heat the chocolate in the microwave, but if you feel you must then heat it with the cream in bursts of no more than 30 seconds, stirring after each go.

You can also use a double boiler but the microwave is probably easier from what your experience seems to dictate.

3.25%milk
Cocoa powder
Melted chocolate (bain marie)

The cocoa will make it thicker

Smaller pieces, microwave at lower power, repeat if necessary and stir using residual heat to melt it.

cravingchronicles.com/2013/01/17/rich-creamy-5-minute-microwave-hot-chocolate-for-one/

I know I'm doing it wrong but I just make a roux and add my chocolate powder and then milk until I get desired consistency.

a what like you get at a bar? beer?

lol

Who the fuck orders hot chocolate at a bar?