Place cut side down on a baking tray. Bake for 40-50 minutes until soft.
Meanwhile slice bacon width wise into strips. Add to a frying pan and saute' until the bacon is crispy and brown. Then remove bacon to a paper towel and drain.
Saute' onion until translucent in a tablespoon of the bacon grease. Add garlic and saute' until soft.
Allow squash to cool enough for you to handle. Once squash is cool shred with two forks to form the 'spaghetti'.
Once you remove the squash, toast the walnuts in the oven for about 5 minutes, turn and toast another 5 minutes.
Mix spaghetti, and all the rest of the ingredients, except nuts in a large bowl.
Once mixed, place the squash mixture in one side of the squash skin.
Bake squash long enough to heat through, about 15 minutes.
Sprinkle with the toasted walnuts and serve hot.
Notes
Leftovers can be refrigerated for 3-4 days. Reheat in microwave or, covered, in 350°F oven for about 20 minutes, until hot.