Whisk together the flour, baking powder and set aside
In the bowl of a stand mixer, beat the eggs, sugar, and salt on medium-high (KitchenAid 5?) with the paddle until the mixture is pale and doubled in volume, probably 7+ minutes. WHILE THAT'S BEATING....
Start melting the butter and chocolate together in a small saucepan or make a double boiler over a water bath.
Turn the stand mixer to low and add the oil and vanilla just until mixed in. Stop the mixer.
When the chocolate and butter are melted, remove from heat and whisk in the cocoa powder until completely combined and no dry spots remain.
Turn the mixer back on and add the warm chocolate-butter to the frothy egg mixture and mix just until melded.
Add the flour mixture and mix just until combined.
Let everything just sit for a bit. Have a coffee.
Preheat oven to 350℉ / 180℃
Line 2 sheet pans with parchment paper. If you have 3 sheet pans, you're rich and have the staff line them with parchment paper.
Use a 1-tablespoon scoop to drop heaping scoopfuls onto the parchment a couple of inches apart. Should be able to get 10-12 per sheet pan.
Optional: If using the toffee pieces, press the scoopful down a bit and add a large pinch of the toffee pieces to the top. Or, if you so choose, add a teaspoon of peanut butter and use a toothpick to kinda mix in.
Bake 8-10 minutes until puffy and cracked, rotating half-way through. Edges should be firm.
Let cool on the pan while the next pan is baking and remove to a wire rack to cool completely.