To make the dip, heat the flour, mustard
powder and milk in a small saucepan and
gently cook, whisking constantly, until
smooth. Carry on bubbling and stirring
until thickened. Turn off the heat, stir in
the cheese until melted, then season to
taste. Scrape into a microwave-proof
bowl and put some cling film directly
on the surface.
Heat oven to 220C/200C fan/gas 7.
Spread the fries on 1-2 big baking trays
and cook for 10 mins, then scatter over
the Parmesan and garlic salt – use tongs
to toss and coat all the chips in the
cheese, then carry on baking for 10 mins
more until golden and crisp – if the chips
aren’t crispy enough, increase oven to
240C/220C fan/gas 9 for a few mins.
Gently reheat the dip in the microwave
until warm, stir in the chives and serve
with the hot chips.