Shake with ice and strain into a Collins glass containing 2 oz soda water. Top with crushed ice and garnish with a mint sprig and 2 borage flowers (if available). Floating a barspoon of funky Jamaican rum like Wray & Nephew or Smith & Cross would not be out of place here (originally intended but left out of this drink of the day recipe). As for the mint syrup, a tea made from a steep with hot simple syrup, but muddling mint sprigs in simple syrup and straining will work well.
Appears in Maggie Hoffman's 2019 Batch Cocktails: Make-Ahead Pitcher Drinks for Every Occasion book.
For a drink of the day at Loyal Nine, I decided to make a mashup of two popular summer drinks -- namely a cross between a Mint Julep and a Pimm's Cup. From the Julep, I kept the Bourbon, mint, and crushed ice aspects and I considered floating a barspoon of Jamaican rum which is a technique called for in a few late 19th century drink books (I left it out since I figured that the extra ingredient would confuse the verbal description of the drink by servers at the tables); and from the Pimm's Cup, I kept the Pimm's, lemon, soda, and borage flower garnishes.