Core pineapple (leaving a few inches of fruit at the bottom to make an oversize vessel). Freeze overnight in a Ziploc bag.
Put a small amount of ice in a cocktail shaker. Add bitters, demerara syrup, falernum, pear brandy, apricot liqueur, lemon juice, pineapple juice, and bourbon.
Shake and strain into the cored and frozen pineapple. Add crushed ice; stir with a swizzle stick or long spoon. Add more crushed ice and garnish as desired (pineapple leaves, orange slices, bendy straws, umbrella…)
* To make demerara syrup: heat sugar with water over low in a small saucepan, stirring to dissolve. Let cool. Keep refrigerated.