Caramelize the white chocolate: Add the white chocolate to a medium heatproof bowl and microwave in 45-second intervals, stirring between, until golden brown in color and completely melted and smooth.
2. Step
Pour half of the melted chocolate onto a parchment paper-lined baking sheet and spread into an even layer. Freeze for 30 minutes, or until solid. Reserve the remaining melted chocolate.
3. Step
Preheat the oven to 350˚F (180˚C). Line baking sheets with parchment paper.
4. Step
Make the cookie dough: In a medium bowl, combine the butter, granulated sugar, brown sugar, and vanilla extract in a bowl and beat with an electric hand mixer until fluffy.
5. Step
Add the egg and continue beating until fully incorporated.
6. Step
Add the reserved melted white chocolate and beat to combine.
7. Step
Sift in the flour, baking soda, salt, and espresso powder,l and fold into dough until no dry spots remain.
8. Step
Chop the frozen white chocolate into chip-size pieces. Fold into the cookie dough.
9. Step
Scoop the dough onto the prepared baking sheets, 6 cookies per pan, and bake for 12 minutes, until golden.
10. Step
Make the filling: In a large bowl, combine the butter, powdered sugar, espresso powder, cinnamon, allspice, nutmeg, heavy cream, vanilla, and marshmallow fluff, and beat with a hand mixer until well combined and fluffy.
11. Step
To assemble the pies, spread 2-3 tablespoons of filling on the flat sides of half of the cookies. Sandwich with the remaining cookies.
