Heat your skillet over medium-high heat and add the ground beef once it's hot. Break it apart with your spoon as it cooks, which helps it brown evenly and cook faster, roughly 5 to 6 minutes until no pink remains.

Once the beef is fully cooked, transfer it to a clean plate using a slotted spoon. Leave about a tablespoon of the beef drippings in the pan, as this fat carries flavor into your sauce.

Add the diced onion to the remaining drippings in the skillet and cook over medium heat for about 2 minutes. The onion will soften and become fragrant, adding depth and sweetness to the cream sauce.

Add the butter to the pan with the onions and let it melt completely. Once melted, sprinkle the flour over the butter and onions, then stir constantly for about 1 minute until you have a paste. This roux is the thickening base for your sauce.

Slowly pour in the milk while whisking continuously to prevent lumps from forming. Keep whisking until the mixture is smooth and no streaks of flour remain.

Add the salt, pepper, and garlic powder to the sauce and stir to combine. Taste the sauce and adjust seasoning as needed, keeping in mind that the beef will add additional salt.

Add the cooked ground beef back into the sauce and stir until everything is well combined. Reduce the heat to low and let it simmer for 2 to 3 minutes, allowing the flavors to meld together. The sauce should be creamy and thick enough to coat the back of a spoon but still pourable.

While the sauce simmers, toast your bread slices until they're golden and crispy. This creates the perfect texture to hold the creamy sauce without becoming soggy.

Place two slices of toasted bread on each serving plate and pour the creamy beef sauce generously over the top. Sprinkle with fresh parsley if you'd like a pop of color and freshness.