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℃.