Preheat the oven to 350F. Line your baking dish with parchment paper or very generously oil you dish. This is super important to prevent sticking!
Pour the Espresso Layer into the baking dish. Cover with aluminum foil and bake until the top has just set ~15 minutes. If it hasn't, bake for a few minutes longer. After the Espresso Layer has set, pour in the Middle Layer. Cover with aluminum foil and bake until the top of that has set. Finally add the Milk Layer, cover & bake until that has set.
Let the mochi cool for at least 4 hours, ideally overnight. If you cut the mochi too soon, it will be too sticky to handle.
Transfer the mochi to an oiled surface. Oil a knife and cut the mochi into bars of your desired size. The mochi can be pretty sticky so make sure to oil and re-oil the knife as you are cutting. Alternatively, instead of using oil you can roll the mochi in corn starch or tapioca starch. Aesthetically the layers won't look as defined but the mochi won't stick together.