INGREDIENTS
1 1/2 lb
Celery root
2 tsp
Chives or flat-leaf parsley, fresh
1 1/2 lb
Russet potatoes
1/2 cup
Shallots
1 tsp
Thyme, fresh
1 tsp
Dijon mustard
2 tsp
Kosher salt
1/4 tsp
Pepper, freshly ground
1 tbsp
Olive oil
1
Butter, Unsalted
2 cups
Heavy cream
1 oz
Parmigiano-reggiano cheese, grated
4 oz
Gruyère cheese, shredded