Pre-heat oven to 350. Line a standard 12 cup muffin tin with paper cups. Line an 8 inch square pyrex dish with parchment paper and grease.
Mix canola oil and butter, add cocoa and stir until well blended.
Beat eggs with a mixer. Add sugar and vanilla, beat well. Add flour and salt. Stir in chocolate chips.
Fill the muffin tins about 3/4 of the way full, using about half of the brownie batter. Spoon the other half into the prepared pyrex dish.
Bake the cupcakes for about 8-10 minutes and the pan brownies for about 18-23 minutes. Allow to cool completely before frosting. Using the parchment paper lift the brownies from the pan and allow to cool before cutting into shapes.
Frosting: In the bowl of a stand mixer with a paddle attachment (or an electric handheld mixer), add the peanut butter, confectioners sugar, butter, vanilla and salt. Mix on medium-low speed until creamy and smooth. Slowly add the cream and beat on very high speed until the mixture is light and fluffy.
To assemble the cupcakes take the cooled brownies and using a 1 inch heart shaped (or any other fun shape you may desire) cookie cutter and cut out 12 hearts. Frost or pipe as desired and top each cupcake with a heart.
* if you do not want to make brownie hearts, just use the remaining batter to make 12 more cupcakes and double the frosting recipe.