Begin by measuring out all your ingredients, ensuring everything is within reach for a smooth cooking process. Soften the unsalted butter by leaving it at room temperature for about 15 minutes. Preheat your oven to 375°F (190°C).

In a large skillet over medium heat, melt the softened unsalted butter, stirring gently until bubbly. Gradually whisk in the all-purpose flour, garlic powder, salt, and black pepper to form a smooth paste. Cook this roux for about 2-3 minutes until it turns a light golden color.

Reduce the heat to medium-low before slowly whisking in the whole milk, adding it in one cup at a time to prevent lumps from forming. Continue stirring for approximately 5 minutes or until the gravy thickens and coats the back of a spoon.

In a greased 9x13-inch baking dish, carefully cut and place the refrigerated biscuit dough into pieces, evenly distributing them across the bottom. Pour the thickened gravy over the biscuits, ensuring they are nicely covered.

Transfer the assembled casserole into your preheated oven and bake for about 25-30 minutes, or until the biscuits are golden brown and the gravy is bubbling around the edges.

Once out of the oven, let the casserole sit for a few minutes before serving. Consider garnishing with freshly chopped parsley or a sprinkle of shredded cheese.