Place a heat proof bowl over a pot with boiling water. Make sure the water doesn't touch the bottom of the bowl.
Add in the chocolate chips and allow them to melt, stirring occasionally until smooth.
Take the bowl off the heat and immediately stir in the peanut butter. Whisk until fully incorporated.
Alternatively, you can melt the chocolate chips in the microwave. Add them to a microwave-safe bowl and heat in 15 sec increments until chocolate is fully melted, making sure you stir after each one.
Transfer your chocolate mixture into the prepared pan, and smooth out the tops into an even layer. Sprinkle with salt flakes if desired.
Freeze for at least 1 hour, or until completely firm.
Slice into squares or triangles and enjoy!
Store in the fridge for up to 1 month or freeze for up to 3 months.