Mix the flour, baking soda, pumpkin pie spice, and salt together in a medium bowl.
Beat the butter and sugar together with an electric mixer. Add the rest of the wet ingredients while it mixing.
Then scrape the bowl and add the flour mixture a little at a time.
Once the dough has come together, divide it onto two pieces of plastic wrap. Wrap the dough into two disks and refrigerate for at least 30 minutes.
Remove one disk from the fridge. Flour a work surface and roll it out to between 1/8 -1/4 inch thick. Cut out the cookies as close together as possible. Use a spatula to transfer the cookies to parchment paper-lined cookie sheets. The dough is fragile, so if you lose an appendage, gently press it back together. Remember, fragile dough = light tender cookies.
Gather the leftover dough and repeat. Try to get as many cookies cut out of two rolls on each disk. The more you gather and re-roll, the tougher the dough gets!
Bake for 10-15 minutes. Allow to cool. Raise the oven rack to the highest position and turn on the broiler.
Using a piping bag, or a freezer bag with the corner cut off, spread the marshmallow fluff over each cookie. The goal is to get a smooth layer about a 1/3 the thickness of the cookie. If you add too little is will get bumpy when you toast it, and if you add too much, it will run off. I used about a tablespoon per puppy cookie.
The marshmallow fluff will smooth out after a minute or two. To create the effect of an ear, place one more dollop of fluff on the head, right before you place the cookies under the broiler.
Toast the cookies under the broiler for about 30 seconds. DO NOT take your eyes off them! Marshmallow fluff burns fast! Once the come out, quickly add the eyes to your puppies!