Put 1/2 cup boiling water into a quart-size saucepan. Add butter and beat until butter melts. Add flour all at once, and stir vigorously until ball forms in center of pan.
Remove from heat and let stand 5 minutes.
Add eggs, one at a time, beating after adding each egg. Mixture should be very stiff.
Drop by spoon onto a greased cookie sheet (you should divide the dough to make about 18 puffs).
Bake in preheated 375 degree F oven until free from beads of moisture, about 40 to 45 minutes. After baking, cool on a wire rack before filling with cream.
While the puffs are baking, make the cream filling. In a saucepan, mix sugar, flour, and salt. Add scalded milk gradually. Cook 15 minutes, stirring constantly until mixture thickens. Once mixture thickens, stir occasionally.
Add eggs, slightly beaten, and cook 1 minute more.
Cool and add vanilla extract.
Cut the top off the cooled puffs and fill with cooled cream filling.
Replace top. I sometimes dust these with powdered sugar before serving.