Place margarita salt (or sugar) on a plate. Rub a lime wedge around the outer edge of the glass. Roll the rim of the glass in the salt to coat the rim.
In a cocktail shaker filled with ice, combine tequila, Grand Marnier, lime juice and agave nectar. Shake well.
Strain into a margarita glass or coupe glass.
Slowly top with champagne. Add a dash or two of orange bitters on top.
Garnish with a lime wedge or wheel.
Notes
If you want to make a big batch ahead of time, you can mix together the tequila, triple sec, lime juice and agave nectar. Then all you’ll have to do is add some of that mixture to a glass and then top them up with champagne.Here are the ingredient amounts for 8 drinks: