6Tbspbuttermilk (or milk with 2 tsp lemon juice; let sit for 10 min)
Powdered Sugar
Filling:
3/4cupheavy cream
2/3cuppowdered sugar
2/3cuppeanut butter
1(1/2 cup) stick of butter, room temperature
3/4cuppowdered sugar
Instructions
For the cake: Beat eggs until frothy & pale. Combine sugar, salt & vanilla. Add to egg mixture & beat until blended well.
Sift flour, cocoa, baking powder together twice & fold into egg mixture. Whisk the oil & buttermilk together & fold into chocolate mixture. Pour into a parchment lined jelly-roll pan. (I spray the bottom of the pan to keep my parchment paper in place & grease & flour the sides too.)
Bake at 350*F for 10-15 minutes or until the cake springs back when touched. Let sit for 1-2 minutes after removed from oven. Flip cake over onto a powdered sugar dusted towel. Roll up & let cool completely.
To make filling: In a stand mixer whisk heavy cream until frothy & gradually add ⅔ cup powdered sugar. Whisk until stiff peaks are formed. Place whipped cream in a separate bowl. Wash & dry mixing bowl.
Using the paddle attachment now, whip peanut butter & butter together until light & fluffy, scraping bowl as necessary. Add ¾ cup powdered sugar all at once & blend until incorporated. Fold prepared whipped cream into the peanut butter buttercream.
Unroll cake & spread filling evenly. Roll back up, cut & serve. Keep refrigerated.