Cut squash neck into 1/2-inch thick slices. Halve the remaining squash and remove seeds and strings. Slice 1/2-inch thick. Season generously with salt and pepper. Heat a heavy 12-inch skillet over medium-high heat. To check when hot enough, add a large drop of water (1/8 teaspoon) to the skillet. When it rolls around the pan like a bead of mercury it is ready.Advertisement
Remove skillet from heat; add oil. Swirl to coat bottom of skillet. Return to medium-high heat. Add half the squash (don't crowd the pan). Cook for 2 1/2 to 3 minutes or until a crust forms (be patient; squash will release when ready to be turned). Turn and cook for 4 to 5 minutes more or until squash is crusted and tender, reducing the heat to medium, if necessary, to prevent overbrowning.
Remove squash from skillet to a serving platter; cover loosely and keep warm. Repeat with remaining squash, adding additional oil if needed. Remove skillet from heat. Carefully add broth, juice, and garlic (mixture will spatter). Return to heat. Bring to boiling, stirring to scrape up browned bits. Boil gently, uncovered, for 5 minutes or until reduced by about half. Remove from heat. Whisk in butter and sage.
Spoon sauce over squash to serve. Top with additional sage, if desired.