Cast the molds with the tempered chocolate, tap out excess chocolate from molds and scrape away excess.
Place face down on parchment paper to set, then place in the refrigerator for 10 minutes.
Remove from the refrigerator and set aside until ready to fill.
To make the ganache:
Place the glucose, cream and mint leaves in a saucepan and bring to a simmer. Remove from heat, cover and steep for 5-10 minutes, depending on how strong you like it.
While the mint is steeping, melt the chocolate partially over a double boiler. You can also do so using a microwave, but it's not my preference.
Remove from heat and pour the cream mixture through a sieve, over the partially melted chocolate. Use a whisk to stir (not whisk) until the mixture is fully combined and smooth.
Allow the ganache to cool to about room temperature and stir in the butter and extract unit well combined. Allow to cool before piping.
Assembly:
Pour the ganache into a piping bag and snip a small opening at the tip of the bag.
Fill each mold with the ganache and allow to set (overnight is best, but 3-5 hours will also work depending on the temperature conditions in your home).
If leaving them as half spheres, be sure not to fill all the way to the top, so that they can be easily capped.
If joining the two halves, you can be a little more liberal with the filling. You will need to slightly warm the edges of each half sphere and gently press them together to create the spheres.
Notes
You likely won't be making hundreds of truffles, so I've scaled down the recipe to yield approximately 30 truffles.