Add the sugar and water to the instant pot and mix well.
Secure the lid, close the pressure valve, and cook for 11 minutes at high pressure.
Add the room temperature butter slices, white chocolate chips, milk powder, and vanilla extract to the pot and quickly stir until well combined.
Add the 15 chopped cookies and fold them in until combined.
Pour the mixture into a parchment-lined 8x8 inch pan with 1-inch overhang of parchment and smooth it out with a spatula if needed. Top with the remaining 2 chopped cookies.
Let the fudge cool down on a wire rack (white chocolate cools down quickly, this should take about 5-10 minutes), then put it in the fridge for 3 hours to set.
Lift from the pan using parchment then cut into small squares.
Store fudge in an air-tight container in the fridge for 2-3 weeks, or in the freezer for a few months.