Preheat oven to 350F. Spray and line your 9x13 pan with parchment paper so you can easily lift the cake out after baking and cooling.
Whisk all the dry ingredients together well in a large bowl. Make sure to whisk out any lumps in the cocoa powder.
In a separate bowl, whisk together all the wet ingredients.
Add the wet ingredients to the dry ingredients, whisking as you go. Mix everything until there are no pockets of dry flour left. The batter will be very thin.
Pour the batter into your prepared pan and give the pan a couple or sharp raps on the counter. Bake for 30-35 minutes, or until the center springs back when lightly touched. (You can also ue a toothpick test.) This cake bakes quickly.
I let the cake cool for 15-20 minutes in the pan, then gently lift it out (using the parchment paper as handles) to a cooling rack. Let it cool completely on the rack. Note: the cake can be made the day before.
peanut butter filling
Use electric beaters to cream the 4 Tbsp salted butter, softened, 2/3 cup creamy peanut butter *, and 1 Tbsp vanilla extract. Add the 2 cups powdered sugar and 7 Tbsp half and half, and beat until smooth and fluffy. Add a bit more half and half if your filling is too thick. Add extra salt to taste if needed.
assemble the cake
Slice the cake in half crosswise and remove the parchment paper from the bottom. Place one half on your serving plate, flat side up.
Spoon the peanut butter filling on the cake and gently spread out to the edges. There will be a generous amount!
Place the second half of the cake on top of the filling, flat side down.
chocolate glaze
Put the 1 cup dark or semi sweet chocolate with the 1/3 cup heavy cream and 2 Tbsp butter in a microwave safe bowl and microwave for one minute. Let sit for 2 minutes, then gently stir to melt the chocolate until the mixture is thick and glossy with no lumps.
Let the glaze cool for a few minutes to thicken up, then gently pour the ganache over the top of the cake, nudging it towards the sides with the back of a spoon. It should just start to drip down the sides.
Let the ganache set up before serving. Refrigerate the cake if not serving right away.
To serve slice the cake into squares or rectangle slices. I like to slice the whole thing in half, and then slice each half. Any way you slice this cake, it's delicious :)
Notes
Use a creamy style peanut butter, and avoid natural style brands where the oil separates out from the nut butter.
Nutritional information is provided as a courtesy and is an estimate only. This information comes from online calculators. Although The View from Great Island attempts to provide accurate nutritional information, these figures are only estimates.
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