Line a 9x9 pan with parchment paper, leaving overhang on the sides and set aside.*
Crush Oreo cookies into fine crumbs using a zip-top bag and rolling pin or use.a food processor.
Reserve ½ cup Oreo crumbs for the ice cream filling.
Combine remaining Oreo crumbs with melted butter until the mixture resembles wet sand.
Firmly press half of the Oreo mixture firmly into the prepared pan using the bottom of a measuring cup.
Freeze the crust while preparing the filling.
In a large bowl, combine heavy cream, vanilla, sweetened condensed milk, and malted milk powder, and beat with a hand mixer until stiff peaks form.
Gently fold in the reserved Oreo crumbs to create a cookies-and-cream ice cream filling.
Spread filling evenly over the chilled crust and smooth the top.
Freeze for 1 hour until the top is set.
Sprinkle remaining Oreo crust mixture over the top and gently press into an even layer.
Sprinkle fleur de sel finishing salt over the top.*
Freeze at least 4 hours or overnight.
Lift from pan using parchment paper and slice into 8 rectangles.
Let them sit at room temperature for about 10 minutes before serving for the best texture. Individually wrap any leftovers in plastic wrap for a grab-and-go treat.