In the work bowl of a food processor, combine spinach, basil, pecans, cheese, vinegar, garlic, salt, and pepper; pulse until finely chopped. Add olive oil in a slow, steady stream, pulsing until smooth.
To build 1 sandwich, spread 1½ tablespoons spinach mixture in a thin, even layer onto 1 bread slice. Layer with 3 turkey slices; add another 1½ tablespoons pesto mixture, spread in an even layer. Top with another bread slice and repeat layers once; cover with a third bread slice. Repeat with remaining bread slices, spinach mixture, and turkey.
Using a serrated knife, trim edges of sandwiches to create 3 rectangles; cut each lengthwise into 3 rectangular tea sandwiches. Serve immediately. Garnish with basil, if desired.
Recipe by Southern Lady Magazine at https://southernladymagazine.com/turkey-pesto-tea-sandwiches-recipe/