Hasselback Butternut Squash with Yogurt and Garlic Butter

This dish makes a stunning main course for a vegetarian meal, or a really special side for a holiday feast. I served it as the main course, along with some whole wheat couscous with garlic and kale. 
INGREDIENTS
for the butternut squash

• Olive oil
• 1 butternut squash, peeled, halved lengthways and seeds scooped out
• Salt

for the yogurt

• 1/3 cup greek yogurt or sour cream
• juice of 1/2 a lemon
• 1 garlic clove, smashed then minced very small
• pinch of salt
• 1-2 tbsp extra virgin olive oil

for the garlic butter

• 7 Tbsp unsalted butter
• 2 large garlic cloves, finely chopped
• Pinch chili flakes, optional
• A few sprigs of parsley and/or cutting celery or celery leaves (I used a combination), finely chopped
• Pinch of salt

Instructions

1. Preheat the oven to 425. Drizzle a little olive oil on a baking sheet.
2. Put the butternut squash half cut side down on a chopping board between two large chopsticks or wooden spoon handles. Cut down in 1/5 inch intervals, ensuring you don’t cut through all the way. The chopsticks/spoon handles will stop the knife going all the way through. Repeat with the other half. You’ll need a large and sharp knife to do this! FYI, if you’re struggling with this step (sometimes butternut squash are tricky to cut, read the note below!).
3. Season the squash liberally with kosher salt  and pepper on both sides and drizzle with olive oil. Place the squash cut side down on the baking tray then put it in the oven until the squash is tender and edges slightly crisp. This will take about 1 hour, but depending on the size of your squash it could be a bit quicker or take longer!
4. Blend the yogurt, extra virgin olive oil, lemon juice, garlic, and salt.
5. For the garlic butter, in a small pan over a low-medium heat, melt the butter with a pinch of salt then add the garlic and chili flakes. Cook for two minutes, or until the garlic is golden. Remove from the heat then stir in the chopped herbs, reserving a few herbs to sprinkle fresh on top.
6. Spoon the yogurt onto a serving dish/large plate, add the squash, then pour over the garlic butter. Top with fresh herbs if desired.
7. NOTE: If you’re struggling with cutting the squash when it's raw, then the other option is to cut the squash after it's roasted for about 15 minutes. To do this: season the squash liberally with kosher salt on both sides and drizzle over olive oil. Place on a baking tray then roast the squash whole for 15-18 minutes, until softened slightly. Remove from the oven and place on a chopping board. Then, cut the squash as instructed above. Return the squash to the baking tray, scored sides up and continue roasting.