Cheesy Kale Gratin Recipe

1 tsp pepper

1 cup heavy cream

6 cups kale

2 cups onions

4 tbsp unsalted butter

1/2 tsp ground nutmeg

1 cup grated gruyere cheese

1/4 cup all purpose flour

2 cups whole milk

1 tbsp kosher salt

2 cups freshly grated parmesan cheese