For the chocolate ganache: Heat the heavy cream until just boiling. While that is warming pour the baking chips into a glass bowl. Pour the cream over the chocolates and allow to sit for 5 minutes. Stir until smooth and allow to slightly set up (5-10 minutes).
For the frosting: Whip the butter until light and fluffy. Stir in the powdered sugar and vanilla until combined. Add the marshmallow fluff and mix until incorporated.
Match your macaron cookies with fitting sized partners. Spread the marshmallow frosting on one side. Dab a bit of chocolate ganache on the other. Gently press together and serve.