Preheat oven to 375 degrees; spray a standard 12-cup muffin tin with nonstick spray.
1. Combine the flour, salt, baking soda and spices by whisking together in a large mixing bowl.
2. In another large mixing bowl, beat together the maple syrup, melted butter, eggs, vanilla extract, and pumpkin puree. Add the walnuts and stir the wet ingredients into the dry inredients with a few swift strokes.
3. Dollop batter into muffin cups (an ice cream scoop is helpful). Bake in center of preheated oven about 20-30 minutes of until centers of muffins are firm and bouncy to the touch.
4. Cool on a rack for 10 minutes, then remove muffins from pan. Serve muffins warm with sweet butter. Can be made one day ahead - cool the muffins completely on the rack, then wrap in a plastic bag. Hold muffins overnight at room temperature or freeze for longer storage (up to two months). To reheat cooled or thawed muffins, unwrap and place on a baking tray in a 325-degree oven for 10 minutes.
1 1/2 cups flour
3/4 tsp salt
1 tsp baking soda
1/4 tsp nutmeg
1/4 tsp cinnamon
1/4 tsp allspice
1/4 tsp ginger
3/4 cup maple syrup
1/2 cup melted butter
1 tsp vanilla extract
1 Cup pumpkin puree (or 1/2 cup pumpkin puree and 1/2 cup chopped apples)