1. 1. In a medium saucepan, combine the chopped apples, 1/4 cup water, and lemon juice. Cook over medium heat, stirring occasionally, until the apples are soft and tender, about 10-15 minutes.

2. 2. Use an immersion blender or food processor to puree the cooked apples until they are smooth and creamy.

3. 3. In a separate bowl, whisk together the sugar, whole eggs, and egg yolks until the mixture is well combined and the sugar has dissolved.

4. 4. Slowly pour the apple puree into the egg mixture, whisking constantly to prevent the eggs from curdling.

5. 5. Return the mixture to the saucepan and cook over low heat, stirring constantly, until the apple curd thickens and becomes smooth, about 10 minutes. If using cornstarch, mix 1 tablespoon cornstarch with 2 tablespoon water to make a slurry, then stir it into the curd before cooking.

6. 6. Remove the apple curd from the heat and let it cool completely. Once cooled, transfer it to jars or airtight containers and store it in the refrigerator until ready to use.