01 -
Microwave the milk for about 4-5 minutes until just under the boiling point.
02 -
In a medium saucepan, melt the butter and add the flour. Cook together for 2 minutes, then slowly pour in the scalded milk while whisking constantly.
03 -
Cook the mixture until the sauce begins to thicken. Add the lemon zest, Dijon mustard, savoury, and season with salt and pepper. Stir in the parmesan cheese, then remove from heat.
04 -
Arrange the cod fillets in the bottom of a greased 9x9 inch baking dish or individual gratin dishes. Pour the prepared sauce evenly over the fish.
05 -
Top the dish with shredded cheddar cheese. Mix the cracker crumbs with olive oil and sprinkle them over the cheese. Optionally, add ½ teaspoon of savoury to the crumbs.
06 -
Bake the dish at 350°F (175°C) for 45-60 minutes, or until bubbling and the top is evenly browned. If using individual gratin dishes, bake for 25-30 minutes, checking the center to ensure the fish is fully cooked.