Heat oven to 400°.
Heat milk and margarine to rolling boil in 2-quart saucepan.
Stir in flour.
Stir vigorously over low heat until mixture forms a ball, about 1 minute; remove from heat.
Beat in eggs, all at once; continue beating until smooth and thickened.
Beat in 1/2 cup of the Gruyere cheese and the Parmesan cheese.
Drop 3/4 of the dough by tablespoon-fuls into 8 mounds in a circle onto greased cookie sheet.
(Each mound of dough should just touch the next one.) Drop a teaspoonful of remaining dough onto center of each mound.
Sprinkle with remaining 1/4 cup Gruyere cheese.
Bake on center oven rack until ring is puffed and golden, 40 to 45 minutes.