Preheat oven to 350˚F. Place parchment paper onto a cookie sheet and set aside.
Melt semi sweet chocolate chips in the microwave. Cool.
In a large bowl, cream together the butter and sugar. Mix in eggs, 1 at a time until combined. Add cooled, melted chocolate chips and vanilla. Mix until smooth.
Combine the flour, baking powder and salt in a small bowl. Gradually add flour mixture to the chocolate mixture. The dough will seem sticky but thats how you want it. Add 3/4 cup milk chocolate chips and chopped pecans.
Scoop dough onto the cookie sheet with an ice cream scoop. Flatten each slightly so there is a flat surface to place marshmallows on. Bake 8 minutes.
Pull cookie tray out and place about 4-5 mini marshmallows on top of each cookie and press down. Place back into the oven for another 2-3 minutes or until marshmallows are slightly brown and fluffy.
Cool cookies on the cookie sheet for a few minutes before transferring them to a wire rack to cool completely. Repeat steps with remaining dough.
Using a microwave safe bowl, melt the remaining 3/4 cup of chocolate chips. Pour into a disposable piping bag and cut the tip off. Drizzle chocolate over the cookies.