-
1
Cook onion in butter in a deep 12-inch heavy skillet over moderate heat, stirring occasionally, until golden, about 10 minutes.
-
2
Add squash, garlic, salt, and white pepper and cook, stirring occasionally, until squash is just tender, about 15 minutes.
-
3
Remove from heat and stir in parsley, sage, and nuts.
-
4
Cool filling.
-
5
Cook garlic in butter in a 3-quart heavy saucepan over moderately low heat, stirring, 1 minute.
-
6
Whisk in flour and cook roux, whisking, 3 minutes.
-
7
Add milk in a stream, whisking.
-
8
Add bay leaf and bring to a boil, whisking constantly, then reduce heat and simmer, whisking occasionally, 10 minutes.
-
9
Whisk in salt and white pepper and remove from heat.
-
10
Discard bay leaf.
-
11
(Cover surface of sauce with wax paper if not using immediately.)
-
12
Preheat oven to 425F.
-
13
Toss cheeses together.
-
14
Spread 1/2 cup sauce in a buttered 13- by 9- by 2-inch glass baking dish (or other shallow 3-quart baking dish) and cover with 3 pasta sheets, leaving spaces between sheets.
-
15
Spread with 2/3 cup sauce and one third of filling, then sprinkle with a heaping 1/2 cup cheese.
-
16
Repeat layering 2 more times, beginning with pasta sheets and ending with cheese.
-
17
Top with remaining 3 pasta sheets, remaining sauce, and remaining cheese.
-
18
Tightly cover baking dish with buttered foil and bake lasagne in middle of oven 30 minutes.
-
19
Remove foil and bake until golden and bubbling, 10 to 15 minutes more.
-
20
Let lasagne stand 15 to 20 minutes before serving.
