1. Place chilies on a small baking sheet and broil 3 to 4 inches from heat, turning as needed, until chilies are charred and blistered all over, 10 to 12 minutes. Cool. Remove and discard skin, stems, and seeds. Coarsely chop chilies.
2. In a 6- to 8-quart pan, combine mangoes, chilies, and lemon juice.
3. Mix pectin with 1/4 cup sugar. Stir into mangoes. Stirring, bring to a rolling boil over high heat. Add remaining 3 3/4 cups sugar and stir until mixture returns to rolling boil. Stir and boil exactly 1 minute longer. Remove from heat.
4. Ladle into clean canning jars to within 1/8 inch of top. Wipe jar rims. Set clean, flat lids on top. Screw on bands. Invert jars for 5 minutes, then turn upright. Let cool at least 24 hours. Check seals by pressing firmly on centers of the lids. If a lid pops back, it's not sealed; store it in refrigerator.
Nutrition analysis per tablespoon.