This should be done ahead of time, since you want the pan to set and cool for at least 20 or 30 minutes before adding in the mixture. I use an aluminum pan (Mirro brand – the kind you find at all grocery stores). It measures about 8 inches across the top, 6-1/2 inches across the bottom, and about 4-1/4 inches deep. It also has a removable plastic handle which can be easily unscrewed from the pan.
Add ½ cup of the sugar to the pan and use medium heat to melt the sugar until it caramelizes. Be careful not to burn the sugar! Keep shaking the pan so that all the sugar melts. Once the sugar is a nice light brown color and melted, turn the pan so the liquid coats the sides, about 2-1/2 to 3 inches up from the bottom. Set the pan aside and let cool down (about 20 to 30 minutes) .
In a large mixing bowl, blend the remaining ingredients (1 cup sugar, eggs, evaporated milk, vanilla and ginger extract). For best results, use a hand mixer to get a better consistency. Note: the original recipe calls for ¼ teaspoon of vanilla extract only, I’ve modified it by also adding (or replacing it with) ginger extract.
When you add the mixture to the carmelized pan, pass it thru a sieve so that any little pieces of egg or whatever doesn't get into the mixture. It is normal to hear a crackling sound when the cold mixture is being added to the the pan, if it is still a little warm.
Pre-heat the oven to 350 degrees. Make sure to unscrew the pan’s plastic handle before placing it into the oven!
Place the pan in a "double boiler". Fill a large baking pan with about an inch or so of water. Place the other pan in the center. Place both pans onto the center oven rack. Cook for about 1 hour, then begin checking if done.
Probably the most difficult part of making Quesillo is knowing when it is done. If you don’t cook it long enough, it will fall apart (cave in) when it is served; if you cook it too long, it will come out dry and grainy. You should be able to insert a clean knife about ½ way from the edge of the pan, and the center, and pull it out dry. The center should still be a little runny. After it is chilled, that runny part will firm up.
The following picture is an example of what the knife will look like before it is done.
In my oven, it usually takes about 1 hour and 15 minutes to completely cook. Different
ovens may vary. I always start checking after about an hour. Once you've made a few
quesillos, you should have a better idea.
Carefully cover the the pan with foil. Set aside and let pan cool. Place in refrigerator over night, to chill.