01 -
Preheat your oven to 350 degrees F. Line an 18x13 inch half sheet pan with parchment paper or grease it well with butter or nonstick spray.
02 -
In a medium saucepan, melt 1 cup butter and 1 cup water over medium-high heat. Add 2 cups brown sugar and stir occasionally until it reaches a rolling boil. Remove from heat and let it cool for a couple of minutes.
03 -
Add 2 teaspoons vanilla to the butter mixture. Add 2 cups flour, then add salt and baking soda. Stir the salt and baking soda into the flour before mixing everything together. Use a whisk to incorporate fully, removing any lumps.
04 -
In a small bowl, whisk together 2 large eggs and 1/2 cup sour cream. Add this mixture to the batter and stir until smooth and fully combined.
05 -
Pour the batter into the prepared pan and spread evenly to the edges. Bake in the preheated oven for 17-20 minutes, or until a toothpick inserted in the center comes out clean. Let the cake cool for 20 minutes.
06 -
In a clean saucepan, melt 3/4 cup butter with 3 and 1/2 cups brown sugar, 1/2 cup + 1/3 cup evaporated milk or heavy cream, and 1/4 teaspoon salt. Bring to a rolling boil over medium heat, stirring constantly, until the mixture thickens enough to coat the back of a spoon. Remove from heat and stir in 1 and 1/2 teaspoons vanilla.
07 -
Place the saucepan with the icing into an ice water bath, being careful not to let water into the icing. Stir constantly for 3-5 minutes to cool and thicken, making sure the edges of the pan are scraped to prevent hardening.
08 -
While the icing is still pourable, spread it over the slightly cooled cake and smooth it to the edges. Let it set for a few minutes before serving.