Herb Syrup
First make the herb syrup as this will need to infuse for at least 1/2 an hour.
Heat equal parts of sugar and water over a medium heat until all the sugar has dissolved. Not too hot or the sugar will burn before the syrup has formed.
Take off the heat, add the rosemary and allow to infuse for at least 1/2 an hour or overnight in a fridge if you want a stronger flavour. With strong flavoured herbs such as rosemary, fennel etc 1/2 an hour should suffice but if you want to make a simple floral syrup using rose petals or something similar then a longer steeping time will help.
Pear Juice
In Autumn it is lovely to use up any gluts of pear or slightly soft pears to create your own pear juice. Just peel and core and blend with the lemon juice ( or lime juice is equally good) to stop it going brown. You might need to loosen with a splash of water to allow it to blend smoothly. Pears have a tendency to be granula to the taste so it is also worth sieving after blending.
If you simply can’t be bothered then use tinned pears (but in pear juice rather than syrup or it will be too sweet). Drain and blend thoroughly.
From here it becomes a little subjective and entirely dependant on your personal taste so best have a bit of an experiment if you are planning on using this for an autumnal wedding.
The rule of thumb is two parts pear juice to one part syrup tossed with ice cubes into your cocktail shaker and thoroughly shaken but this is all according to taste and further ice cubes and chilled sparkling water can be added to make this into a long refreshing autumn drink.
Alternatively ditch the sparking water and replace with a good slug of gin or vodka for something more naughty.
Serve with a sprig of flowering rosemary and a slice of ripe pear.