If you don't have bottled root beer syrup, combine 1 cup of strong brewed sarsaparilla/root tea concentrate (or 1 cup root beer), 1 cup granulated sugar and 1/4 cup molasses in a small saucepan. Warm gently until sugar dissolves, simmer 5 minutes, cool and strain. The recipe here uses 3/4 cup of that syrup. Alternatively use commercial root beer concentrate or reduce 1 cup canned root beer by simmering to 3/4 cup.

Have simple syrup ready (1:1 sugar to water). If not ready, dissolve equal parts sugar and hot water and cool.

Assembly

Build the drink

Fill a highball or Collins glass about 3/4 full with ice (roughly 1 cup). Pour in the root beer syrup (3/4 cup) and simple syrup (1/4 cup) over the ice.

Add the dark rum (2 oz) and bourbon (1/2 oz). Add 1/2 tablespoon fresh lime juice to brighten the flavors.

Stir gently with a bar spoon 6–8 times to combine syrup and spirits with the ice.

Top and finish

Top the mixture with 6 oz chilled club soda for effervescence, pouring gently down the spoon to preserve bubbles. Then float 2 oz chilled root beer on top by pouring slowly over the back of a spoon to create the appearance and aroma of a classic root beer bottle pour.

Express the orange peel over the drink (pinch to release oils), rub the rim of the glass with the peel and drop it in as garnish. Add a maraschino cherry if desired.

Serve with a straw and a long stirrer so guests can mix the float in if they prefer a sweeter, cream-soda finish.