For the biscuits, pre-heat the oven to 165°C. Place the butter and sugars into a mixing bowl on a mixer with the paddle attachment and mix until all the butter is fully incorporated. Add in the eggs one at a time followed by the dry ingredients. Spoon tablespoons of the mixture onto a lined tray with a 3 cm gap between biscuits. Bake at 165°C for 9-11 minutes. Remove from the oven and cool at room temperature. These can be eaten as they are or made in advance and stored in an airtight container.
For the filling, melt the milk chocolate in the microwave in 30 second increments, stirring in between. Continue until the chocolate is melted and warm. Combine the dollop and thickened cream and add one third and combine it with the peanut butter and then add in the melted chocolate. Fold the remaining cream and mix until combined.
To assemble, place a small amount of the prepared chocolate mousse into the base of a jar or glass and top with a biscuit. Add layer of mousse about a third of the way up and top with another biscuit. Repeat this process again. Top the last biscuit with some mousse to fill to the top. Leave in to fridge for 4-5 hours to allow the biscuits to soften. Place a spoonful of dollop cream on top and sprinkle with roasted chopped peanuts to serve.