In a 3-quart saucepan over high heat, add potatoes and squash chunks with water; add 1 teaspoon salt. Bring just to boil; reduce heat to medium, cover, and cook until tender, approximately 12 to 15 minutes.
In a small frying pan or saucepan, add 2 tablespoons of the butter and the sage. Tilting pan and watching closely, cook about 3 minutes, until butter foams and begins to brown; remove from heat and keep warm.
When potatoes and squash are cooked, remove from heat and thoroughly drain the water off.
Reduce heat to low, return pan with the drained potatoes and squash to burner, and shake 1 to 2 minutes; remove from heat.
Roughly mash with hand masher leaving mixture chunky. Gently mix in remaining 1 tablespoon butter and enough milk for consistency desired. Season with salt and pepper.
Spoon into a large serving bowl and drizzle with brown butter/sage mixture.
Makes 4 servings (about 4 cups).
* Butternut squash is easily found in supermarkets. Beige colored and shaped like a vase or a bell. This is a more watery squash and tastes somewhat similar to sweet potatoes. It has a bulbous end and pale, creamy skin, with a choice, fine-textured, deep-orange flesh with a sweet, nutty flavor. Some people say it is like butterscotch. This squash weighs from 2 to 5 pounds. The oranger the color, the riper, drier, and sweeter the squash.
Browned Butter Smashed Potatoes with Butternut Squash Recipe: https://whatscookingamerica.net/Vegetables/SmashedPotatoesSquash.htm