1. Preheat your oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish with olive oil or butter.
2. In a large skillet, heat 2 tablespoons of olive oil over medium heat. Add the chopped onion and sauté for about 5 minutes until translucent and fragrant.
3. Add the minced garlic and sliced mushrooms to the skillet, cooking for another 5 minutes until the mushrooms release their moisture and begin to brown.
4. Add the ground beef to the skillet, breaking it up with a wooden spoon. Cook until browned and no longer pink, about 7-8 minutes. Season with salt, pepper, smoked paprika, and dried thyme.
5. Stir in the thawed peas and cook for another 2 minutes. Remove the skillet from heat and set aside.
6. In a separate saucepan, melt the butter over medium heat. Whisk in the flour and cook for 1-2 minutes to form a roux, stirring constantly to avoid browning.
7. Gradually whisk in the milk, continuing to stir until the sauce thickens and becomes creamy, about 5-7 minutes. Season with a pinch of salt and pepper.
8. To assemble the casserole, layer half of the sliced potatoes evenly on the bottom of the baking dish.
9. Spread half of the meat and vegetable mixture over the potatoes.
10. Pour half of the creamy sauce over the meat layer, then sprinkle with half of the shredded cheese.
11. Repeat the layering with the remaining potatoes, meat mixture, creamy sauce, and cheese. For an extra golden crust, sprinkle the Parmesan cheese on top if using.
12. Cover the dish with aluminum foil and bake in the preheated oven for 40 minutes.
13. Remove the foil and bake for an additional 15 minutes, or until the top is bubbly and golden brown.
14. Let the casserole rest for about 10 minutes before serving to allow the layers to set.

I always remind Olivia and Isabella to keep an eye on the bubbling cheese—there’s something so rewarding about that golden crust that signals a meal well made. It’s these simple pleasures that make cooking together so memorable.