Preheat oven to 425°F. Cook spelt in a large saucepan of boiling salted water until tender, 25–35 minutes. Drain.
Meanwhile, toss squash with 1 Tbsp. oil in a baking tray; season with salt and pepper (could add a bit of chilli flakes). Turn squash cut side down and roast until browned and tender, 20–30 minutes.
Bring pine nuts and remaining 4 Tbsp. oil to a very gentle simmer in a small saucepan over medium, stirring occasionally. Reduce heat and cook at a very low simmer until nuts are light golden brown, about 5 minutes. Remove from heat and whisk in garlic and miso. Let cool (it will look a bit chunky and broken at this point). Add vinegar and 1 Tbsp. chives and whisk until dressing is smooth and emulsified; season with salt.
Toss spelt with a generous tablespoonful of dressing on a large platter.
Top with the squash. Place radicchio and apple on top and drizzle remaining dressing over and top with chives.