Make sure your butter is softened before starting anything. Preheat your oven to 400 degrees.
Get your miso butter mixture ready by adding 7 tbsp butter, 2.5 tbsp miso paste, 1/2 tbsp rice vinegar, 2 small cloves of garlic (minced) to a bowl and mix well until a paste forms.
Cut your cabbage into 1/8ths (wedges) and place onto a baking sheet. Do this by cutting half first, lay flat side down and cut in half again, and then half one more time.
Using a pastry brush, brush the miso butter all over the cabbage - both sides (top and bottom), and the back, basically cover them in miso. Save about 1 tbsp of the miso butter to brush after baking. Bake at 400 degrees for 40-50 minutes until cabbage is roasted and fork tender.
While baking, make your toasted breadcrumbs. Melt 1 tbsp of butter over low/medium heat. Add the breadcrumbs and toast until gold brown, stirring frequently to avoid burning. This is a quick process! Once golden brown, turn off heat and let cool.
In a food processor, add 1/2 cup shelled pistachios, a handful of parsley, and 1 tsp red pepper flakes (you can eyeball all of this. I promise regardless of your amounts, it'll taste good). Give this a couple pulses until nuts are roughly chopped! Set aside.
Once cabbage is done roasting, remove from oven. Transfer to a serving platter. Using that last 1 tbsp of miso butter, brush that on while still hot to get nice and melty. Sprinkle your breadcrumbs on top and garnish liberally with your pistachios + parsley. Serve warm and enjoy!