1. Grate zucchini and place in colander. Sprinkle with some salt to drain excess water. Let sit 10 minutes.
2. Meanwhile, whisk egg yolk with splash of milk and have brush nearby. Preheat oven to 400 F.
3. Slice the mushrooms. Then, heat a saute pan with 1 Tbsp. olive oil, thyme and 2 peeled garlic cloves, and stir fry mushrooms for 7-10 minutes, or until they turn golden brown and shrink. Season with salt and pepper. You want most of the water/moisture to evaporate from them. When done, take them out and place on a side plate. Remove garlic and thyme. Keep the pan to cook the zucchini in the next step.
5. After zucchini is drained, squeeze out excess water. Then, heat olive oil with 1 clove garlic and add in zucchini. Cook in medium heat a couple minutes till it turns bright green. Remove garlic clove. Let cool a few minutes.
6. Get the puff pastry and roll it out just a bit with a rolling pin. For one large filet, don’t cut it. Place cooled mushrooms on pastry. Then, place salmon on top of mushrooms. Season salmon with a pinch of salt and pepper. Place cooked and cooled zucchini on top. Close up pastry folding it over itself. Make decorations on top with extra pastry if you like.
7. Mix 1 egg yolk with a splash of milk to brush on the pastry. Brush egg-milk mixture all over pastry and sprinkle sesame seeds on top.
8. Bake 30-40 minutes or until golden brown. Turn halfway through. When a rich golden brown, take it out. You can also use a thermometer and test that it reaches at least 145 F. Carefully with a large spatula or two spatulas, lift and pace on a cooling rack to keep it from getting soggy. Wait 5-10 minutes before serving.
Serve with salad and cherry tomatoes for a fresh touch. Enjoy.