Slice the button mushrooms very thinly using a mandolin or a sharp knife. Prep the rest of your veggies and lay them out on a tray.
Fill a deep edged baking tray with room-temperature water. Immerse 1 rice paper wrapper in the water for about 10 seconds. Pull it up out of the water, allow the excess to drip off and lay it flat on a clean work surface.
Place sliced mushrooms in two rows along the centre and just below the centre of the wrapper. Top with 3 to 4 basil leaves. Now place an even mix of the rest of your veggies along the bottom row of mushrooms. Leaving gaps on the side of the wrapper.
Fold the bottom of the wrapper over the filling, tightly tucking it in as you go. Fold in the sides and continue to tuck and roll until you have sealed the wrapper and have a neat cylinder. Place the summer rolls in between two clean and damp dish cloths. Repeat with the remaining wrappers and filling.
Slice summer rolls in half before serving on a platter. Sprinkle them with some sesame seeds and serve them alongside the mango dipping sauce.