Combine the water, sugar and dried hibiscus in a small saucepan and bring to a boil over high heat. Stir occasionally until the sugar has melted. Remove from the heat and let cool to room temperature.
Place a fine mesh strainer over a glass jar and pour the simple syrup through the strainer to remove the hibiscus flowers. Seal the jar with a lid and refrigerate until cold.
ASSEMBLE THE MARGARITA:
RIM THE GLASS WITH SALT:
Fill a cocktail shaker with ice. Add the tequila, simple syrup, Grand Marnier and lime juice.
Dip the end of a toothpick into the simple syrup, until a drop forms on the tip. Brush the drop of simple syrup over the very edge of the glass (you don't want too much, just enough to make the salt stick (Note:When it's just my husband and I, he dips a clean finger into a small dish of syrup and runs the tip of his finger around the glass.) Turn the glass over and dip the rim into the Margarita salt to add a thin salt garnish to the glass. Set aside.
Fill a cocktail glass with chipped ice and set aside.
Fill a cocktail shaker with ice. Add the tequila, simple syrup, lime juice and Grand Marnier. Seal the shaker with the lid and shake aggressively until the outside of the shaker is icy cold.
Strain the shaken margarita into the glass filled with ice and top with sparkling water. Garnish with a slice or wedge of lime and serve.
FOR A PITCHER OF MARGARITAS: (MAKES 8)
In a small pitcher, combine the tequila, simple syrup, lime juice and Grand Marnier. Refrigerate several hours until ice cold or overnight.
To serve, rim the glasses with salt as described above. Fill the glasses with ice and add half a cup of margarita mix to each glass and top with 2-3 ounces of sparkling water. Garnish with a lime wedge or slice and serve.