1 to 2 ounces (less if you want a stronger, more tart cocktail) pineapple juice
1 ½ ounces fresh lime juice
Splash of club soda or seltzer water, if desired
Kosher salt, to rim the glasses, optional
Instructions
In a large pot, heat sugar, vanilla, and ginger over medium heat until sugar begins to melt and turns an amber color, about 5 to 8 minutes.
Add the pineapple and stir. (at this point the caramelized sugar will probably seize up; this is OK, keep stirring it over medium heat and the sugar will dissolve completely in about 5 to 10 minutes)
Once sugar has dissolved, add the water and bring to a boil, then reduce heat to low to simmer. Cover the pot and cook, stirring occasionally, until pineapple looks deflated, about 20 to 30 minutes.
Add the vinegar, remove from heat and let stand for at least 2 hours or up to overnight. Strain through and sieve or fine mesh strainer and refrigerate until cold.
For the cocktail: In a cocktail shaker, combine the tequila, Cointreau, Amaretto, pineapple shrub, pineapple juice and lime juice with ice. Shake well a strain into two glasses rimmed with kosher salt (if desired) and filled with ice. If desired, finish the drink with a splash of club soda. Garnish with a lime wheel or pineapple slice.
Recipe by Allons-Eat! at https://www.allonseat.com/caramelized-pineapple-shrub-pineapple-margaritas/