Fill a 12-16 oz mason jar or cocktail shaker completely with ice.

Add the syrups and espresso to the ice-filled jar or shaker, then screw on the lid tightly to ensure liquid won't leak out.

Shake vigorously until the whole jar is completely chilled and cold to the touch, and the liquid is very bubbly and foamy (about 10-20 seconds).

Pour the mixture into a separate glass (or drink straight from the mason jar), and add the oatmilk. Start with 6 oz, then add more if desired. Add more ice if needed.

For a sweeter beverage, add more syrups to taste. For less sweetness, use less syrup to begin with or use sugar-free syrups.