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At what point did you whip the Jello with cornstarch - after dissolving in water, when it was starting to firm, etc.?
Do you remember any other ingredients, such as corn syrup, powdered sugar, egg whites, etc.?
It looks like you went offline without seeing my request for more information. I spent some time combing through my grandma's old cookbooks and recipes. Cornstarch does not whip well with anything water-based unless the liquid is hot. Even then, it often clumps. Egg whites or corn syrup are what are usually whipped with Jello to make these marshmallow confections. The squares are then rolled in a mixture of cornstarch and powdered sugar so they won't be too sticky. More modern recipes jsut use the powdered sugar because it already contains cornstarch. I'll share two of the recipes I found. You can try them and see if they compare to the one you remember.
3 small packages of Jello 3/4 cup water, divided 2 cups granulated sugar 2/3 cups light corn syrup 1/4 teaspoon salt 1 tablespoon vanilla extract 1/4 cup powdered sugar 2 T cornstarchLightly grease a 9 x 9-inch baking pan. In a large mixing bowl , sprinkle the Jello over 1/2 cup cold water and allow it to dissolve for about 5-10 minutes.Combine sugar, corn syrup, and 1/4 cup water in a small saucepan. Bring the mixture to a very hard boil and cook for one minute. Make sure you stir it frequently.Pour the boiling syrup on top of the Jello and begin whisking on high. Add the salt and whisk on high for about 10 minutes. At about 8 minutes in, drop a small dollop on the counter to test how close it is to done. If within 30-60 seconds, it starts to firm up like you would imagine a marshmallow would, you can stop whipping. Ten minutes is usually enough; you can go as long as 12 if you’re unsure.At the end of the mixing, add the vanilla . Allow the marshmallows to set until firm – usually about 4-5 hours.Once firm, combine 1/4 cup powdered sugar and 2 T cornstarch in a bowl. Use a pair of kitchen scissors to cut the marshmallows into cubes. It helps prevent sticking if you dip your scissors in the powdered sugar mixture between each cut. Toss each marshmallow in the powdered sugar mixture.
1 package Jello (3 0z. size)
2/3 cup boiling water
1 cup sugar
3 tablespoons light corn syrup
Powdered sugar/ cornstarch mixture
Dissolve Jello in boiling water. Reduce heat. Stir in sugar until dissolved (without boiling it). Blend in corn syrup. Then chill until slightly thickened.
Line an 8 inch square pan with wax paper and grease with butter. Beat the gelatin mixture at high speed until soft peaks form. Pour into prepared pan. Refrigerate overnight.
Heavily dust a cutting board with powdered sugar/cornstarch. Invert the pan on the cutting board. The wax paper can be peeled off easily if you dampen it and let it stand a few minutes. Dust the top pf the Jello mixture with powdered sugar/cornstarch, then cut into one inch squares. Roll cut edges in the sugar/cornstarch mixture.
I hope one of these will work for you.
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