<b>CAKE:</b>  Preheat the oven to 350 degrees F.  You can use either one 8" or 9" round pan with higher sides, or two shorter round pans.  Whatever you choose, grease it and I usually put a little parchment paper in the bottom for good measure.

In a large stand mixer with paddle attachment, beat together the peanut butter, oil, and brown sugar, until combined and creamy.

Add the vanilla extract and eggs (one at a time), and beat just until combined.

Add 1/2 cup of the flour and the baking powder, soda, and salt, mixing just until combined, then alternate adding the buttermilk and remaining flour (beating in-between additions), until everything has been JUST mixed in...be careful not to mix too much or the cake will be dry and dense.  If using the peanuts, throw those in and give it a quick mix as well.

Pour the batter into the pan or pans and bake until a toothpick comes out moist but clean.  That will be 20-30 minutes if you're using two pans, and probably 30-40 if you're using one pan. 

Remove from the oven and let the cake(s) sit in the pan for 10 minutes, then invert onto a wire rack to cool COMPLETELY.

<b>GANACHE:</b>  When your cake is mostly cool, heat the cream in a small saucepan until it's steaming---but don't let it boil or burn!  Remove from the heat and add the chocolate pieces. 

Whisk consistently, starting in the middle to get the chocolate to melt and emulsify into the cream.  Be patient, it will look weird and watery and grainy at first, but eventually become glossy and thick.  Sprinkle with some large sea salt crystals (if desired) and set aside to solidify but still be spreadable (about 30 minutes).

<b>FROSTING:</b>  Beat the butter in your stand mixer or with an electric hand mixer, then add the peanut butter and beat for about 30 seconds to combine it. 

Add the powdered sugar a little at a time and a pinch of sea salt (taste to get the right balance), and beat that in until fluffy. Add 1 tablespoon of the cream or milk (if needed). Chill if not using right away.

<b>ASSEMBLE:</b>  Cut the cooled cake in half horizontally (or get your two separate layers).  Put a layer down and then spread your chocolate ganache in a thick layer over it, going right to the edges.  

Put the top layer on and then carefully smooth a thick layer of frosting on the entire cake.  You can choose to color some of the frosting (or, I'd recommend, some regular white frosting) if you want to pipe other decorations on it.