Preheat oven to 400 degrees F. Lightly grease two large baking sheets; set aside.
In a medium saucepan, combine the water, butter, garlic salt, and nutmeg. Bring to a rapid boil. Add flour all at once, stirring vigorously. Cook and stir until mixture leaves the side of the pan and begins to form a ball. Remove from heat; cool for 10 minutes.
Add eggs one at a time beating after each addition with a wooden spoon until smooth. Stir in 1/2 cup of the cheese and the membrillo.
Place dough in a pastry bag fitted with a large star tip. Pipe dough (about 1 tablespoon each) into 40 mounds on prepared baking sheets (or drop dough by small spoonfuls onto prepared baking sheets). Sprinkle with the remaining 1/4 cup cheese.
Bake on separate oven racks for 16 to 18 minutes or until golden brown, rotating baking sheets between oven racks halfway through baking time. Transfer to wire racks; cool completely. Place in a single layer in a plastic freezer container and freeze. Attach serving directions to gift (below).