Split the squash, lengthwise or crosswise, in half. Scrape out and discard the seeds. Cut off a thin slice from the bottom of each half so that it will rest firmly upright in a pan.
Melt 2tablespoons butter and brush the rims and cavity of each squash with it.
Blend the sugar and ginger, and sprinkle each half, rim and cavity, with equal portions of the mixture. Arrange the halves on a baking sheet and bake1 hour.
Meanwhile, put the peas into a sieve and run hot water over them for 15 seconds, or until defrosted. Put the peas in a small skillet. Add remaining 1tablespoon butter, mint, salt, and pepper. Cook briefly until heated through. Do not overcook.
Fill the squash halves with the peas and serve immediately.