Preheat oven to 350°. Bake pecans in a single layer in a shallow pan 8 to 10 minutes or until toasted and fragrant, stirring halfway through. Cool completely (about 20 minutes). Reduce oven temperature to 325°.
Process cheese and butter in a food processor 10 to 15 seconds or until creamy, stopping to scrape down sides as needed. Add flour and next 3 ingredients; pulse 9 to 10 times or until mixture is crumbly. Add toasted pecans; pulse 9 to 10 times or until combined.
Transfer mixture onto plastic wrap on a flat surface; gather dough into a ball, and flatten into a 1-inch-thick disk. Wrap in plastic wrap, and chill 1 hour until firm, or seal wrapped dough in a zip-top plastic freezer bag, and chill up to 3 days.
Turn dough out onto a floured surface. Roll to 1/8- to 1/4-inch thickness. Cut with 1 1/2- and 2-inch leaf-shaped cutters. Place on parchment paper-lined baking sheets.
Bake at 325° for 16 to 18 minutes or until golden brown. Transfer to a wire rack; let cool 15 minutes.
Note: You can also freeze thoroughly cooled, baked shortbread leaves in an airtight container. Store in freezer up to 2 weeks.
Bake shortbread 3 days ahead and store in airtight containers, or make dough, chill up to 3 days, and bake right before your party.