A cocktail shaker would be great, if not, just stir it all up well in a glass.
Instructions
Rhubarb Syrup
Cut up the rhubarb stalks into about 5cm (2in) pieces.
3 large stalks of rhubarb
Grate, chop or pound the ginger, don't peel it, just scrub it clean.
a thick piece of fresh ginger
Place everything into a small saucepan and bring to boil. Then simmer for 10 minutes, by which time, the rhubarb would be very soft and pulpy.
125 ml water, 100 g white sugar
Strain the syrup into a clean jug, pushing down the rhubarb to extract as much of the flavour as possible. For a clearer margarita, don't squash down, just strain the liquid through.
Leave to cool. You can place it in the fridge, if you like.
Rhubarb Juice
If using a juicer, just juice the stalk.
½ rhubarb stalk
If using a chopper, cut up the stalk into 3 pieces and blitz in the chopper.
½ tsp water
Strain, squeezing out all the liquid.
Salt and Ginger Rim
Mix the ginger and salt together and place in a saucer.
1 generous pinch ground ginger, a saucer of fine salt
Serving
Run a lime slice all around the rim of a glass.
Dip the glass rim into the ginger flavoured salt, coating well.
Method One:
Place everything in a shaker, and pour into the glass, minus the ice cubes.
60 ml (2 parts) tequila, 30 ml (1 part) Cointreau or Triple Sec, 30 ml (1 part) Rhubarb Syrup, 30 ml (1 part) fresh rhubarb juice
Serve with a slice of lime on the rim.
lime slices to decorate, a handful of ice cubes
Method Two:
Pour the rhubarb syrup into the glass.
30 ml (1 part) Rhubarb Syrup
Mix everything else in the shaker and pour over the syrup very slowly. You could do it over a spoon if you like, but it shouldn't be necessary, given the density of the syrup. This second method will create the layers as you see in the image. Serve with a little straw or shaker, with a lime on the rim.
60 ml (2 parts) tequila, 30 ml (1 part) Cointreau or Triple Sec, 1 tsp fresh lime juice, lime slices to decorate, a handful of ice cubes
Notes
Total time does not take into account the cooling down of the rhubarb syrup.