To make the infused tequila, use an inexpensive white tequila like Hornitos.
Open the bottle, pour out about 1-1/2 ounces to make room for the serrano peppers, and drink the tequila shot.
(It's part of the recipe!)
Slice the 2 serrano peppers in half lengthwise and stuff them into the bottle of tequila.
After 2 days, strain the tequila and remove the peppers.
To make the cocktail, pour a small amount of sweet & sour into a bowl and dip the edge of a 12-ounce highball glass into the mix and then into the margarita salt and shake off the excess.
Fill the glass with ice, and then pour the tequila, Grand Marnier, sweet & sour and Tamarind nectar into the glass in the order given.
Cut a slit into one edge of a jalapeno pepper slice and garnish glass with pepper.
Prep time does not include time to infuse tequila.