Preheat oven to 375°F. Lightly grease a mini muffin pan and set aside.
Cut brie into 24 even-sized cubes (about ½ inch big). Place diced apples in a small bowl and toss to coat with Challenge Lemon Butter Snack Spread. Set aside.
On a lightly floured work surface, roll out crescent dough to a 10-inch x 15-inch rectangle. Cut lengthwise into 4 even strips, then cut crosswise into 6 even strips. You will have 24 2-½-inch squares.
Gently press each square into a well of the mini muffin pan. Scoop apple mixture into each cup, top with a cube of brie, and sprinkle with ½ teaspoon of walnuts.
Bake until pastry is puffed and corners are golden brown, 12-15 minutes. Let cool a few minutes in the pan, then transfer to a serving dish. Enjoy warm or room temperature.