S'mores Thumbprints

Directions

1. 1
   Heat oven to 350F.
2. 2
   Line cookie sheets with parchment paper; set aside.
3. 3
   Combine butter and powdered sugar in bowl; beat at medium speed until creamy.
4. 4
   Add egg yolk and vanilla; continue beating until well mixed.
5. 5
   Add flour and salt; beat at low speed until well mixed.
6. 6
   Place egg white into bowl; lightly beat with whisk.
7. 7
   Place graham cracker crumbs into another bowl.
8. 8
   Shape dough into 1-inch balls.
9. 9
   (Dough may be soft.)
10. 10
    Dip balls into egg white; roll in graham cracker crumbs.
11. 11
    Reshape balls, if necessary.
12. 12
    Place 1 inch apart onto prepared cookie sheets.
13. 13
    Make indentation in center of each cookie with thumb or back of teaspoon.
14. 14
    Bake 9-10 minutes or until edges just begin to brown.
15. 15
    Immediately place 4 to 5 chocolate chips and 3 mini marshmallows in each indentation.
16. 16
    Immediately return to oven; continue baking 3-4 minutes or until chocolate is melted and marshmallows are puffed.
17. 17
    Remove to cooling racks.
18. 18
    Melt remaining chocolate chips and drizzle over cookies, if desired.