This is the fudge at Hagrid attempted to make for Harry Potter in the first book of the epic book series
Author: Eva Bakes
1cupdark brown sugarpacked
1stick (1/2 cup)unsalted butter
2Tablespoonsblack treacle or dark molasses
1/4teaspooncream of tartar
Generously grease or line a standard 8"x8" square pan and set aside.
In a medium sized saucepan, mix together all of the ingredients except for the vanilla. Heat on medium-high and stir until the butter has completely melted.
Allow the mixture to cook until it reaches 240 degrees F on a candy thermometer. Do not mix during this stage. Once the mixture comes to temperature, remove the pan from the stove and stir in the vanilla.
Let the mixture sit for about 5 minutes.
Now, roll up your sleeves and keep stirring (and stirring and stirring) until the mixture becomes super thick - to the point where you can no longer stir because it's so dense. It will resemble a very thick brownie batter consistency. I took a few breaks here and there to rest my arms, but I would say it took a good 15 minutes or so of constant stirring.
Transfer the fudge to your prepared pan and smooth out the top. Chill in your refrigerator until firm, about 1-2 hours. Slice and serve.