Remove the stems / innerds of your mushrooms, and clean them.
Preheat your oven to 450F while you prepare the filling.
In a skillet, add the sundried tomato oil over medium heat. Once hot, add in your ground beef, shallot, & garlic, and sauté for about 5 minutes.
Then add your sundried tomatoes, chopped walnuts, salt / pepper, and ¼ cup of the broth. Bring to a boil, and reduce to a simmer until thickened.
Right before stuffing the mushrooms, stir in your parsley. Fill each mushroom cap with the filling, and arrange in a baking dish in a single layer. Add your remaining broth carefully around the mushrooms so they can absorb the liquid while cooking.
Place in your oven for 15-20 minutes, until the mushrooms are browned.