Heat oil in a pan on a low-medium heat. Add in onion and cook until translucent, about 2 minutes. Add in garlic and fennel seeds and cook for 1 minute. Add into a mixing bowl with pork, carrot, zucchini, salt and pepper.
Slice each sheet of puff pastry in half and place a quarter of the mixture down the middle. Pat into a long sausage shape. Brush sides of the pastry with whisked egg. Fold both sides of the pastry over into the middle, do as firmly as possible.
Cut into 6 equal lengths and transfer to a baking tray. Brush with more egg mixture and sprinkle with sesame seeds. Repeat this with remaining pastry and place tray into the oven. Bake for 25-30 minutes or until cooked through, puffed and golden.
Failing to extract excess water from grated zucchini causes puff pastry to turn soggy rather than crisp during baking. Moisture management determines whether the pastry layers separate into distinct flakes or dissolve into a dense paste. Grate the zucchini finely and press it through a clean dish towel until no liquid drips before combining it with the pork mince, grated carrot, and crushed fennel seeds. This preparation safeguards the structural integrity of the butter puff pastry sheets. Cooking the diced onion over low-medium heat for two minutes softens the cell walls without browning, preventing sharp, acrid notes from competing with the aromatic garlic. When shaping the filling, pack the meat mixture firmly down the center of each halved pastry sheet to eliminate internal air pockets that cause uneven baking. Brushing the pastry edges with a lightly beaten egg acts as a structural adhesive, sealing the seams securely before portioning into six equal lengths per log. Bake these rolls on a standard rimmed baking tray at 180 degrees Celsius for 25 to 30 minutes until the exterior achieves a deeply golden hue and the internal pork registers a safe temperature. Adapting this formulation for different diets requires careful consideration of ingredient ratios. Replacing traditional pork mince with a plant-based alternative or substituting gluten-free pastry changes the moisture requirements significantly, demanding extra attention during the liquid extraction phase. Unbaked assembled rolls tolerate freezing well on trays before transfer to airtight containers, allowing direct oven baking from frozen with an additional five minutes added to the total timer.