Preheat oven to 400 degrees F.
Season the halved and seeded squash with salt and pepper. Arrange cut sides down on a parchment-lined baking sheet. Roast in the oven for 30 minutes and then flip with the flesh side up.
Drizzle 1 tablespoon of olive oil over the flesh side of the squash. Cover with parchment paper and roast for 15 minutes or until squash is fork tender.
Scoop flesh into a bowl; discard skins. Lightly season with salt and pepper.
While the acorn squash is roasting, over low heat in a small skillet, add 1/4 cup olive oil. Add the sliced garlic and walnuts. Cook, stirring often, until the nuts are lightly toasted and fragrant and the garlic is golden brown. Adjust heat as needed being sure garlic and nuts do not burn. Remove from heat and pour into a small bowl to halt cooking.