Roast Duck Feast (Potatoes Au Gratin and Brussel Sprouts with Caramelized Leeks)

1500g or 4 large russet potatoes, peeled
100g or 1/2c medium sharp cheddar, shredded
100g or 1/2c gruyere, shredded
50g or 1/2c parmesan, finely shredded or grated
5g or 2tsp cornstarch
Salt
Pepper
75g or 1/3c chicken stock
125g or 1/2c heavy cream.

Thinly slice potatoes using mandoline. Set aside.
Shred cheeses and add to a medium bowl with cornstarch. Toss to coat. Layer as follows in an 8”x8” baking pan - each potato layer should be perpendicular to the last:
Layer 1: layer potatoes as shown @3:33. Potatoes should overlap about 30%. Season lightly with salt and pepper.
Layer 2: potatoes, top with ⅕ of the grated cheese mix.
Layer 3: potatoes, season lightly with salt and pepper.
Layer 4: potatoes, Top with ⅕ of the grated cheese mix.
Layer 5: potatoes, Season lightly with salt and pepper.
Layer 6: layer potatoes perpendicular to layer 5. Top with ⅕ of the grated cheese mix.
Layer 7: layer potatoes perpendicular to layer 6. Season lightly with salt and pepper.
Layer 8 - top layer potatoes. Mix chicken stock and cream in a small container and pour mix evenly over the top of the layered potatoes. Finish by topping with the remaining grated cheeses, making sure to fully cover the potatoes.