Squeeze thawed frozen spinach in a clean kitchen towel until completely dry before layering -- excess water is the top reason white lasagnas turn watery and loose.
Cook the flour in the butter for the full 2 minutes until it smells nutty and looks pale gold; undercooking it leaves a raw, starchy taste in the finished sauce.
The lasagna is done when the internal temperature at the center reads 165 degrees F and the edges are visibly bubbling; tent with foil if the top browns before that point.
Rotisserie chicken is a smart substitute for home-cooked chicken: use the breast meat, cubed, and the flavor holds up well through baking.
Assemble the lasagna up to 24 hours ahead, cover tightly with plastic wrap, and refrigerate; add 10 to 15 minutes to the bake time when going straight from cold.
Source: Lisa Humpf ↗ · rated ★ 4.4 by 2,546 people there
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Added to the cookbook by Gaither · Jun 8, 2026 · Last touched by Gaither · Jun 8, 2026