Preheat EVOO in a skillet over medium heat. Add onions and season with salt and pepper. Saute until tender then add 1 Tb sugar and a little crushed red pepper (make sure not to add to much). Continue cooking until carmelized (about 10 minutes). Add garlic and cook about 1 minute. Remove from heat and let cool.
Meanwhile combine goat and ricotta cheeses. Season with salt and pepper to taste.
Layer potato slices across one row of the pan. Layer next row with zucchini and continue alternating until you fill the bottom of the pan. (You may want to season the veggies before starting the cheese layer).
Dollop 1/3 of goat cheese mixture on top of potatoes and zucchini.
Spread half of the onions on top of the cheese.
Repeat 3 layers then top with remaining goat cheese. Pour milk over casserole then top with breadcrumbs and butter cubes.
Bake for about 25-30 minutes, covered with foil. Remove foil and bake about 15 minutes until top is browned. (I increased the heat to 400 for the last few minutes to get a crisper top).