6tablespoonsunsalted butterat room temperature & cut into small cube
1/2cupplus 1 tablespoon buttermilkat room temperature
1/3cupsdark brown sugarfirmly packed
1large eggat room temperature
For the Caramel Drizzle & Topping:
1/3cupdark brown sugarfirmly packed
3tablespoonsunsalted butterat room temperature
2 ½tablespoonsheavy cream
1/3cuppecanstoasted and chopped (optional)
For the Snack Cake: Preheat oven to 350 degrees F. Place oven rack in middle of oven. Lightly spray an 8-inch square pan with nonstick spray, set aside.
In a medium bowl whisk together flour, cornstarch, baking soda and; set aside.
In a large measuring cup, whisk together the buttermilk and vanilla, set aside.
Beat butter with the paddle attachment on medium-high speed until creamy, about 1 minute. Add the sugar and beat until light and fluffy, about 3 minutes. Scrape down the sides of the bowl as needed. Add egg and beat until combined. Add the flour mixture in two additions, alternately with the buttermilk mixture. Begin and end with the flour mixture, and beat after each addition until smooth, about 20-30 seconds.
Scrape batter into pan and smooth evenly using an offset spatula. Plop blackberries evenly on top, reserving about 5 of them; DO NOT press into batter (they’ll sink during baking). Bake for about 20-25 minutes or until a toothpick inserted has just a few moist crumbs. The cake will just have begun to come away from the sides of the pan. Cool pan completely on a wire rack.
For the Caramel Drizzle: In a small saucepan add the brown sugar, butter and cream. Bring to a simmer over medium-high heat. Simmer for 1 minute, whisking often.
Remove from heat and whisk in vanilla and confectioners' sugar until smooth.
Moving quickly so the mixture doesn’t firm up on you, drizzle half of the icing with a spoon over the top of cake. Then quickly sprinkle pecans and reserved berries evenly over top while icing is still wet. Drizzle with remaining icing, which will set up quickly.