Fudgy Brownie Layer 

1. Preheat the oven to 350F(175C). Line a 9×5 inch bread pan with parchment paper. All four sides of the baking pan should be lined with parchment paper. This will make it easier to remove bars from the pan.
2. In a medium mixing bowl, add and whisk to combine the flour, cocoa powder and salt. 
3. In a separate medium mixing bowl, add the chocolate, butter and oil and melt into a smooth mixture over a double boiler or on high in the microwave at 30 seconds intervals. Chocolate mixture should be stirred intermittently to prevent it from not melting properly and/or burning.
4. Set melted chocolate mixture aside to cool slightly as the rest of the ingredients are prepared.
5. In a large mixing bowl, add the eggs and sugar. With a hand-held electric mixer, beat ingredients together at medium speed until mixture doubles in size and takes on a pale yellow appearance, about 3-4 minutes.
6. Mix slightly cooled melted chocolate and vanilla extract into wet batter at medium high speed until all of the chocolate is incorporated, about 30-60 seconds.
7. Reduce mixer speed to low and mix in the flour mixture into wet batter, about 1-2 minutes. Use a rubber spatula to scrape down the sides and base of the bowl before mixing the brownie batter at medium speed for an additional 30-60 seconds. This will help to ensure a properly mixed batter free of any unmixed ingredients.
8. Spoon brownie batter into prepared baking pan and bake for 18-20 minutes rotating the pan halfway through bake time. Brownies are done when a toothpick inserted into the center comes out with a few moist crumbs.
9. Allow brownie to cool completely to room temperature. 

Caramel Sauce 

1. Fill a small bowl halfway with water. Place the bowl and a pastry brush near the side of the stove where caramel sauce will be prepared.
2. Add the sugar, water, and lemon juice (or vinegar) into a medium heavy bottom saucepan under medium low heat.
3. Whisk sugar mixture together until all of the sugar is dissolved and no granules are present, about 1-2 minutes.
4. Dampen pastry brush in the bowl with water. Use a clean kitchen towel to remove excess water if needed.
5. Use the dampened pastry brush to remove any sugar granules from the sides of the saucepan. Dip pastry brush back into bowl with water to remove sugar granules and repeat the process if needed.
6. Increase heat to medium high to bring sugar syrup to a boil.
7. Once sugar syrup starts to boil, refrain from stirring or whisking.
8. Allow syrup to boil until it reaches a rich golden brown (amber) color, about 4-6 minutes. This change in color occurs quickly so watch syrup attentively as it boils to prevent caramel from burning.
9. Remove caramel from heat. Carefully pour and whisk warmed heavy cream into caramel. As the cream is added to heated caramel, the mixture will bubble up profusely. 
10. Whisk in the butter, salt and vanilla extract into caramel sauce.
11. Pour caramel sauce into a heat safe container and allow to cool completely before using. 

Peanut Butter Caramel Layer

1. Roughly chop half of the whole peanuts.
2. In a medium mixing bowl, add the room temperature (slightly thicken) caramel and peanut butter. Whisk ingredients together to combine.
3. Use a silicone spatula to mix peanuts into peanut butter caramel. 

Assembly

1. Spoon peanut butter caramel over cooled brownie. Use a spatula to flatten caramel into an even layer.
2. Evenly sprinkle the remaining whole peanuts over peanut butter caramel and lightly press peanuts into caramel layer.
3. Apply plastic/cling wrap directly over peanut butter caramel and refrigerate bars for 5-6 hours or preferably overnight. Bars are ready to be cut and dipped into chocolate once firm to touch.
4. Use parchment paper to remove peanut butter caramel brownie from the baking pan.
5. Use a sharp knife to cut brownie into 8 equal bars. Transfer bars to a medium parchment lined baking sheet and place the baking sheet in the freezer.
6. Prepare coating by melting chocolate and oil together either over a double boiler or on high in the microwave at 30 second intervals. Chocolate mixture should be mixed as it is melted to help prevent it from burning.
7. Allow chocolate to cool slightly for 6-8 minutes before using.
8. Remove bars from the freezer. Use a fork to bars one at time in melted chocolate.
9. Chocolate coated bars should be transferred back to parchment lined baking sheet. I used a toothpick to help slide chocolate coated bars off the fork and onto the baking sheet. 
10. Place chocolate coated bars back in the freezer to set for 8-10 minutes or until chocolate no longer appears wet.
11. Transfer remaining chocolate to a pastry or Ziplock bag before removing set bars from the freezer. If chocolate no longer has a pourable consistency, simply warm in the microwave on high for 10-15 seconds to restore pourable consistency.
12. Snip the tip (about 1/8 inch) of pastry or Ziplock bag and drizzle chocolate over bars. May use a spoon to drizzle chocolate over bars.
13. Sprinkle sea salt or finely chopped roasted peanuts over bars before serving.