Preheat oven to 350°F. Grease casserole

In a saucepan, melt 3 tbsp butter, add onions and cook till tender stirring occasionally. Add flour, salt & pepper. Continue stirring till smooth & bubbly. Remove from heat and stir in the milk. Bring to boil while stirring.

Arrange potatoes 🥔 in casserole. Pour sauce over potatoes. Sprinkle parsley & cut remaining butter on top of the potatoes.

Cover bake for 30mins then uncover & bake for 1hr 10mins. Let it sit for 🔟minutes before serving.