To cook chestnuts in the microwave, first halve them, and then cook them in 60-second intervals until the nuts easily separate from their shells. Although the flavor is different than chestnuts roasted in an oven or over open flames, you can cook chestnuts more quickly in the microwave.
To halve the chestnuts, first grasp the nut with a towel to safeguard your hands, and then cut them down the middle using pruning shears. This allows the nuts to easily pop out of their shells with a gentle push and eliminates the need to peel hot nuts. Spread the nuts shell-side up on a paper towel to microwave them. Use them right away or keep them for up to one week in the refrigerator or for months in the freezer.