Add milk, butter, sugar and salt to a pot or a saucepan and bring to a boil.
Turn the heat down to medium, then add the flour all at once and stir with a wooden spoon.
Cook, continuing to stir, until the dough starts to peel away from the sides of the pot.
Transfer the dough to a mixing bowl, then whip on medium speed until it's cooled down to lukewarm.
Continuing to beat, add the eggs, one at a time, then add the egg white.
Fill the dough into a large piping bag with a large, round tip and pipe about 20 dollops onto the baking sheet.*
Bake for 20 minutes, then lower the temperature to 325 degrees F. and continue to bake until the puffs are golden-brown, about another 20 minutes.
Let the puffs cool completely, then slice in half horizontally.
For the filling:
Whip all ingredients to stiff peaks.
Fill into a piping bag and fill into the cream puffs.
For the glaze:
Whisk liqueur with powdered sugar and drizzle over the cream puffs.
*20 dollops will make puffs that are about 2.5 inches wide, which is a little bigger than bite size. For smaller puffs, pipe 30 rather than 20 puffs and reduce the baking time at 325 degrees F. to about 10 minutes.