I always make my own boiled condensed milk. To do this, fill sealed jars with regular condensed milk, add water, and bring it to a boil. Simmer for 2 hours, adding hot water if necessary. A slow cooker is convenient for this purpose. It’s advisable to plan ahead and make the boiled condensed milk the day before or a few days in advance.
Be prepared for the fact that you may need more or less flour than indicated in the recipe. Focus not on the amount of flour, but on the desired consistency of the dough.
Ensure that you wash the eggs thoroughly before use, as even apparently clean shells may contain harmful bacteria. It’s best to use food-safe detergents and a brush for this purpose.