Put the powdered mexican chocolate into a coffee mug. (The term 'Mexican chocolate' is vague, but Boyd's Chocolate Mexicano is what I use. Basically, it's spiced chocolate) Add the Bailey's and Schnapps and stir until the chocolate dissolves as much as possible.
If you've mixed your proportions correctly, the chocolate will not fully dissolve, producing a somewhat 'cement mix' consistency and a slight viscosity. This is good. Add boiling water until the mug is approximately 3/4 full and stir again until it smooths out. A little bit of froth should form on the top. This is also good. Add more boiling water to top off the mug and stir briefly but quickly to mix.
If you've done everything right, there should be a light froth on the top and a mint-chocolate aroma. Enjoy while hot.