Take the cucumber and serrano slice and throw em in the bottom of a cocktail shaker or a jar with a tight-fitting lid. Using a spoon or muddler, smash these guys together at the bottom of the glass to help them release all their flavor. Now pour in the mezcal, lime, pineapple juice, agave, and a handful of ice. Now add the other half of the shaker or put the lid on your jar and shake the absolute shit outta this to 1. cool it down and 2. to get all the flavors mixed up and delicious. Strain over 2 cups full of ice and enjoy.