Cut 4 Envy apples leaving the core untouched. Using a cold press juicer, press the Envy apples through the juicer and collect thej uice in a separate container; set aside for multiple uses later.
To make the simple syrup, heat all of the ingredients (including the apple cores)in a small saucepan over medium high heat. Bring to a boil then reduce to a simmer. Stir to dissolve sugar then remove from heat. Let cool completely before straining with a mesh strainer.
In a large pitcher filled with ice, add the gin, apple juice, lemon juice and apple simple syrup. Stir well. Fill four glasses with ice and pour apple gin mixture until glasses are 2/3 full. Top off each glass with club soda and garnish with an apple slice to serve.