Preheat the oven to 350°F. Place the shells on a baking sheet. Toast in the oven for 3-5 minutes per the instructions on the package, then set aside to cool completely.
Meanwhile, in a small microwave safe bowl, melt 1/2 cup of white chocolate chips and 1 Tbsp of heavy cream in the microwave. Melt in 20 second increments stopping to stir each time. Repeat this process until the chocolate is completely smooth. Set aside.
To prepare the filling: In a medium mixing bowl, whip together cream cheese, mojito concentrate, 1/4 cup heavy cream, 1/2 cup powdered sugar and 2 tsp of rum flavoring. (May use Rum in place of extract, if preferred)
Using a hand mixer, whip together for 2-3 minutes until fully combined and the mixture is creamy and fluffy. Whip in white chocolate and lime zest until combined. Chill for 30 minutes.
To prepare the white chocolate drizzle: Just before assembling, melt remaining 1/2 cup of white chocolate with 1 Tbsp of heavy cream in the microwave. Melt in 20 second increments stopping to stir each time. Repeat this process until the chocolate is smooth. Add additional cream 1 tsp at a time, if needed to thin.
Divide chilled filling evenly between the shells. You can do this with a teaspoon, or a piping bag fitted with a large star tip.
Drizzle each tart with melted white chocolate, and garnish with fresh lime zest and a sprig of mint. Keep chilled until serving.