Place the cream cheese, feta, and half & half (single cream) in a large mixing bowl and beat with a hand mixer or immersion blender until mixture is light and fluffy. Set aside.

To make the balsamic glaze, heat the balsamic vinegar in a small saucepan over medium-high heat. Bring to a gentle boil, stirring occasionally, and cook until the liquid is reduced by half and starts to cling to the back of a spoon. Reduce heat to low and keep warm until ready to use.

Using a spoon, drizzle some of the balsamic glaze onto a serving platter and carefully arrange half of the watermelon squares on top.

Transfer some of the whipped feta mixture to a large piping bag fitted with a large round or star tip (or use a plastic sandwich bag with one of the bottom corners snipped off).

Pipe the whipped feta onto each watermelon square on the platter and top each with some fresh basil. Refill the piping or plastic bag as necessary.

Place another slice of watermelon on top of the basil and gently press down to secure.

Top each appetizer with some of the remaining whipped feta and chopped pistachios.

You could use cocktail skewers or wooden toothpicks to secure the appetizers together if you like.

Serve immediately garnished with small sprigs of fresh basil and a light drizzle of the remaining balsamic glaze, if desired. Enjoy!