Soak dried mushrooms for 20 mins in hot water, drain & rinse.
Cook lasagne sheets as per packet instructions.
Heat 1 tbsp olive oil in a frying pan on high heat, add mushrooms when hot & sauté quickly to cook, stirring frequently. You don't really need any seasoning here as the pesto packs a punch.
Layering: if you want, brush the bottom of your dish with some olive oil but I never have a problem with the pasta sticking. Start with a layer of lasagne, overlapping slightly.
Top with half the pesto sauce, scatter half the mushroom mix and pine nuts.
Another layer of lasagne sheets, followed by half the bechamel, mozzarella and parmesan.
Repeat this, finishing with the cheese layer.
Bake in the oven for about 40 - 50 minutes till golden brown and bubbly. Let it rest for 5 minutes before serving.
Notes
Quite often I turn the bechamel into a cheese sauce by adding half the mozzarella to it and stirring till all the cheese is melted. The rest of the mozzarella I scatter as usual.