Preheat oven to 375 degrees F
Grease a 2-2 1/2 quart baking dish with the pat of butter
Rub the cut side of the garlic around the interior of the pan; discard garlic
Mix the 1 tsp salt and 1/2 tsp of pepper
Layer the potatoes in the pan, sprinkling with the salt/pepper mixture between layers.
Melt the 3 tbs butter in a large saucepan over medium-low heat
Mix the chicken stock and the cream together in a large measuring cup or bowl; set aside
Carefully mix the flour into the melted butter--you want a smooth paste, not a lumpy one
Let the flour/butter bubble around the sides
Slowly add the cream/stock mixture, stirring constantly so there are no lumps.
Bring to a boil, reduce heat and simmer for 3-5 minutes
Remove the saucepan from the heat and add the shredded Gouda; stir until cheese is melted.
Pour sauce over sliced potatoes in pan.
Top with the grated Parmesan cheese
Bake at 375 degrees F for 45-60 minutes.
Remove from oven and let the casserole stand 5-10 minutes before serving