Preheat oven to 275 degrees F (135 degrees C). Grease a baking sheet.
Combine 1 1/2 tablespoons butter and 1 tablespoon brown sugar together in a bowl; add cinnamon, ginger, and salt and mix well. Stir pumpkin seeds into butter mixture until evenly coated. Spread seeds in an even layer onto the prepared baking sheet.
Bake in the preheated oven for 15 minutes; check seeds and continue baking for 10 minutes more.
Mix the remaining 2 tablespoons brown sugar and 1 1/2 teaspoons butter together in a bowl and stir onto the pumpkin seeds.
Continue baking seeds until toasted and fragrant, about 10 minutes more.