In a large skillet over medium heat, heat olive oil until hot and add thinly sliced squash. (I used a mandolin) Season with salt, pepper and red pepper flakes. Let it brown before moving around so that it has some color to it, about 10 minutes. Transfer to a bowl and squeeze lemon juice over it. Salt and pepper to taste.
In the same pan, melt butter. Add green onions and garlic and saute for about 1-2 minutes. Add flour and stir until absorbed. Slowly add milk that has been warmed in the microwave stirring after each addition until well incorporated. Add lemon zest, salt and pepper to taste. Let simmer for a couple of minutes, stirring frequently. Remove from heat and add half of the parsley and thyme.
Add cooked pasta, squash, ½ cup of parmesan and all of the mozzarella, stir to combine and place in a baking dish. Top with remaining parmesan.
In a small skillet add 2 tablespoons butter and panko, stirring until brown. Sprinkle over the pasta mixture and bake at 400º for 25-30 minutes until golden brown. Add reserved parsley if desired.
Barbara's Notes + Tips
If you don't have a mandolin, try to cut the squash as thin as possible.
You can use either zucchini or yellow squash or a mixture of both.
This can be made ahead and refrigerated. Remove and let it come to room temperature and then bake as directed.
You can remove a portion before adding the squash if you have non-squash eaters. Place in a ramekin and bake until golden brown. The ramekin will take less time.