Preheat oven to 325 degrees Fahrenheit for a glass dish; 350 degrees Fahrenheit for a metal dish.
Drop the butter in the bottom of a 9"x13" baking dish and pop it in the oven while it's preheating to melt the butter. Remove when the butter is melted, about 7 minutes.
Sprinkle the graham cracker crumbs over the melted butter. Toss with a fork to evenly coat and then press down evenly over the bottom of the dish to make a crust.
Heat the jam in the microwave or a small sauce pan until it's thin and fluid. Pour evenly over the crust.
Sprinkle coconut evenly over the jam layer.
Pour sweetened condensed milk evenly over the top.
Sprinkle with walnuts and white chocolate chips, pressing down lightly to embed them in the milk.
Bake 25-30 minutes, or until mostly set and lightly browned around the edges.
Cool completely before cutting and serving.