Preheat the oven to 425 degrees F. Line 2 baking sheets with parchment.
Toss the butternut squash with 2 tablespoons of the olive oil and some salt and pepper. Transfer to one of the prepared baking sheets and roast until golden brown, 35 to 45 minutes. During the last 5 to 10 minutes of the squash roasting, add the cleaned squash seeds to the other prepared baking sheet and toss with 2 tablespoons olive oil and a large pinch of salt. Roast until puffed and brown, 5 to 10 minutes. Let the squash cool slightly.
Put the garlic in a food processor and process to break it up a little. Add the squash, chickpeas, lemon juice, tahini and some salt and pepper and puree until smooth. With the processor running, slowly drizzle in the remaining 3/4 cup olive oil to incorporate. Taste for seasoning, adding more salt and pepper if desired.
Lower the oven temperature to 350 degrees F. Line a baking sheet with parchment.
Cut the tortillas into shapes with spooky cookie cutters (you may need to stack the tortillas to press the cutters through) and transfer to the prepared baking sheet. Bake until crispy, 12 to 16 minutes.
Top the hummus with a drizzle of olive oil and the roasted squash seeds. Serve with the spooky tortilla chips.