Combine. In a small saucepan, combine water and sugar (or agave). Stir over medium heat, until the sugar is completely dissolved and the mixture is steaming. 

Steep. Turn off the heat and add the fresh mint leaves. Allow the mint to steep in the simple syrup about 15 minutes (set a timer so you don't forget!)

Strain & Cool. Then, strain out the mint and transfer the mint simple syrup to a jar or container. Chill syrup in the refrigerator until completely cool. Mint simple syrup will keep 1 week in the refrigerator. (You'll have about 12 oz. mint simple syrup)

Muddle. Add 1-2 strawberries and 1-2 Tablespoons mint simple syrup to the bottom of your cup. Muddle the strawberries in the simple syrup until mostly smooth. (A few larger pieces are fine, but the finer you can mash them, the easier they'll be to drink.) Add mint leaves to your cup and muddle just 3-4 times to release the essential oils. (It should smell fresh and fragrant)

Build The Drink. Fill the cup about 3/4 full with crushed ice. Add limeade and sparkling water to your cup. Use a straw or drink stirrer to mix the julep for a few seconds, until the glass starts to get frosty.

Garnish with strawberries, lemon or lime slices, and lots of fresh mint!