Add the tequila, coffee liqueur, agave nectar and espresso to a cocktail shaker.
Fill the shaker with ice and give everything a really hard shake for 30 seconds.
Strain the drink into your serving glass. If you have a fine mesh strainer, use both strainers at the same time while pouring it into the glass.
Garnish by floating three coffee beans on the top of the drink, and serve.
Notes
Coffee Liqueur - I used Kahlua liqueur for this drink, which is sweeter than other coffee liqueurs. If you choose a different liqueur like Mr. Black, you may want to add a little extra to get the right sweetness.
Espresso - freshly brewed espresso will allow you to get the best foam layer on top of the drink. You can substitute in some cold brew concentrate, which will taste great but you won't be able to achieve a thick foam layer.