Place 5 clean 250 or 236 mL mason jars in a boiling water canner; fill with water, cover and boil hard 10 minutes to sterilize jars. Boil Snap Lids 5 minutes-not longer-to soften sealing compound.
Crush strawberries one layer at a time. Measure 4 ½ cups (1125 mL) crushed berries into a large, deep stainless steel saucepan.
Measure sugar; set aside.
Combine cocoa and fruit pectin; whisk into berries until dissolved. Stirring frequently, bring mixture to a boil. Add sugar. Stirring constantly, return mixture to a full rolling boil; Boil hard for 1 minute. Remove from heat.
Ladle sauce into a hot sterilized jar within ¼ inch (0.5 cm) of top rim (head space). Using non-metallic utensil, remove air bubbles. Wipe jar rim removing any stickiness. Center Snap Lid on jar; apply screw band just until fingertip tight. Do not over-tighten. Place jar in canner. Repeat for remaining sauce.
Cover canner; return water to a boil. Process – boil filled jars – 10 minutes. Remove jars. Cool undisturbed 24 hours. Check jar seals. Sealed lids curve downward. Remove screw bands; wipe and dry bands and jars. Store screw bands separately or replace loosely on jars, as desired.