Throw the Cucumber slices (that you aren't using for garnish), Coriander, and Simple Syrup into a cocktail shaker and muddle.
Add Tequila, Triple Sec, Lime Juice, and Egg White to the shaker with ice. If you want a frothier cocktail, don't add ice just yet.
If you added ice, shake more than you would usually; you really want to get that Egg White frothed up. If you haven't added ice yet, dry shake for a bit then shake again with ice.
Strain into a Coupe glass.
Garnish and serve. Have fun.