Mix together the pepper and sugar on a small plate, and pour the vinegar into a shallow bowl that is wide enough for the rim of your martini glass. Dip just the rim of the glass into the balsamic vinegar and then into the peppered sugar, turn the glass over and set aside.
Hull the strawberries and muddle (crush) them in the bottom of a cocktail shaker.
Add the rum, lime and simple syrup, stir to extract as much of the strawberry juice as possible.
Pack your cocktail shaker with ice and shake vigorously.
Fine strain into the sugar rimmed martini glass and garnish with a strawberry.
The standard bar ratio is 2:1 sugar to water. Combine 1 cup (250 mL) sugar and 1/2 cup (125 mL) water in a small sauce pot. Gently heat until the sugar is dissolved, let cool and transfer to a clean container until needed. To help prevent crystallization of the sugar you can also add a tbsp (15 mL) of corn syrup or liquid honey to the syrup while cooking. If you make a larger batch than you need, try adding an ounce of vodka to the syrup to help prevent mould or bacteria from growing during storage.