Preheat the oven to 400 degrees F.
Cut 1-inch off the top of each acorn squash and scoop out the seeds. If necessary in order for the squash to sit upright, cut off a small portion of the bottom. Put 1 of the 4 pieces of butter in the cavity of each squash. Set squash on a sheet pan
lined with parchment paper. Set aside.
In a large saute pan over medium heat, brown the ground pork until no longer pink. Remove the meat from the pan, add the olive oil
and saute the onion
, celery, and carrot until they begin to soften, approximately 7 to 10 minutes. Deglaze
the pan with the white wine
Return the pork
to the pan along with the cooked rice
, spinach, pine nuts
, oregano and salt and pepper, to taste. Stirring constantly, heat mixture thoroughly, approximately 2 to 3 minutes. Remove from the heat. Divide the mixture evenly among the squash, top each squash with its lid and bake for 1 hour or until the squash is tender. Serve immediately.