Preheat oven to 450. Cut the (acorn) squash in half. Scrap out the seeds. Cut the squash in quarters, brush the flesh with olive oil and salt liberally. Place in oven until the flesh can be easily pierced with a fork (approx 30 min.). Scrape the flesh from the skin and place in blender, add enough milk to get the contents to spin, about 1 cup. Add 1/2 stick of unsalted butter, cut in smallish pieces. Blend until smooth, scraping down the sides as necessary. Season to taste with salt. Acorn squash puree, approx. four servings.