In a medium mixing bowl, use a hand mixer to combine ½ cup room temperature unsalted butter and 3 ounces of original cream cheese until creamy and smooth.
Scrape down the sides, then slowly add 1 cup of all-purpose flour and mix until just combined. Scrape down the sides again and cover the bowl. Place it in the refrigerator for 1 hour.
Preheat oven to 350 degrees Fahrenheit. Prepare a mini muffin pan with cooking spray.
Remove the dough from the refrigerator and use a 1 Tablespoon cookie scoop to form (24) 1-inch dough balls. Next, place each dough ball into the prepared mini muffin cups and press evenly into the bottom and sides of the muffin cups to form a cup.
In a medium mixing bowl, use a hand mixer to mix 1 large egg, ¾ cup packed brown sugar, 1 tablespoon butter, softened, 1 teaspoon vanilla extract and ¼ teaspoon kosher salt until combined.
Reserve 2 tablespoons of chopped pecans and set aside. Fold in the remaining ⅔ cup of finely chopped pecans.
Fill each muffin cup with 1 teaspoon of the pecan filling. Next, sprinkle 2 tablespoons of reserved pecans over the top of the tassies.
In the preheated oven at 350 degrees Fahrenheit bake for 15 - 20 minutes or until golden brown. Remove from oven, place on a cooling rack, and allow to cool for 5 - 10 minutes.