Preheat your oven to 350 F and line a 8 x 8 baking dish with foil or parchment paper.
In a large bowl, mix the brown sugar and melted butter until fully combined.
Whisk in the egg and vanilla bean paste or exctract.
Mix in the peanut butter making sure the mixture is smooth.
Using a wooden spoon, mix in the flour and salt.
Pour dough into the baking dish and bake for 20 minutes.
While the bars are baking, make the streusal.
In a small bowl, using a fork mix the flour, butter, cinnamon and sugar together.
Toss in the apples and mix into the streusal.
Once the bars have finished the first 20 minutes, take them out of the oven and sprinkle the streusal on top.
Pop them back in the oven to finish baking. About 15-20 more minutes. Insert a knife to make sure it comes out relatively clean. You still want them to be gooey.
Once they are cooled, slice them and drizzle with the caramel.