> 4 tbsp butter, divided
> 4 oz Gruyere cheese
> 1 large russet potato
> 1 cup half & half
> 1 tsp salt
> 1/2 tsp garlic powder
> 3 cups cauliflower florets
> 2 cup broccoli florets
> 1/4 cup panko bread crumbs
> 1/4 cup shelled pistachios, finely chopped
Preheat oven to 400°F. Grease an 8x8-inch baking dish with 1 tbsp butter. Coarsely grate the Gruyère. Peel the potato and very thinly slice.
In a medium saucepan, combine the half & half, 1 tbsp butter, salt, and garlic powder. Season with pepper. Heat to a boil on medium-high, stirring occasionally. Add potatoes and cook 2–4 min., until slightly thickened, stirring occasionally.
Transfer half of potato and half & half mixture to prepared dish. Top with half of the cauliflower and broccoli. Sprinkle half of Gruyère on top. Repeat layering: potato mixture, cauliflower and broccoli, and Gruyère. Bake 20 min.
Meanwhile, in a medium microwave-safe bowl, melt remaining 2 tbsp butter in the microwave. Add the bread crumbs and pistachios. Stir to combine.
Sprinkle panko mixture over gratin and bake another 15–20 min., until vegetables are tender and crumbs are golden brown.