First, brew the coffee using a stovetop espresso maker (3-cup size) or a pod machine to make 3 cups. The coffee should be milder than usual.
In a bowl, combine the mascarpone and sweetened condensed milk and soften with a spoon. Add the heavy cream and beat with an electric mixer until thick and smooth.

Transfer the cream to a piping bag with a large tip (if you don't have a tip, just cut the end of the bag).
Dip the puff pastry cookies quickly in the coffee and arrange them in a rectangular dish (I used a 11x8 inch (28x21 cm) dish) or baking pan. Pipe small mounds of cream onto the cookies. Add a second layer of dipped cookies and cream, then finish with a dusting of unsweetened cocoa powder.

Refrigerate the tiramisù with puff pastry cookies for at least 1 hour before serving.