1. In a skillet, heat 1 tbsp olive oil and fry the garlic until fragrant. Cook onion until soft and add beef, tomato. Stir-fry until meat is no more pink.
2. Add all ingredients A and bring to a boil. Reduce the heat to low. Cover and simmer for about 20min. Remove the lid and cook for about 10min more. Let it cool and set aside.
3. *Make white cream* Melt the butter over medium heat in a medium saucepan, then add the flour. Stir continuously until the mixture is smooth. Reduce the heat to medium-low and add the milk (a little at a time), stirring constantly. The mix will be a doughy paste at first. Keep adding milk gradually (avoid lumps). When all milk is added, reduce the heat to low to simmer, stirring constantly for a few more minutes until the sauce has thickened. Season with salt.
4. Spread a spoonful of the meat sauce and white sauce over the base of a baking dish. Arrange the zucchini, cover with pasta sheets. Repeat the layers : white sauce, meat, zucchini, pasta, twice more. Finish with meat sauce and then, last, white cream sauce.
5. Sprinkle grated cheese. Pre-heat the oven to 190℃.