Lay your hands on empty screwtop jam jars. Clean them & rinse w/ hot (very hot - almost boiling!) water. Use a fresh tea towel for drying.
Trim the pineapple - only use very ripe, but not brownish parts. Chop everything as small as possible & put 750 g in a bowl.
Trim the ginger - only use juicy soft parts. Chop as small as possible & put 150 g aside.
Put the limoncello & the ginger & part of the pineapple in the blender & blend.
Add rest of the pineapple & blend again. Take care that some small pieces stay alive - or spare them the blending.
Pour the mess in a pot, add the sugar & mix thoroughly.
Bring to a boil & boil for about 4-5 min accruing to the preserving sugar rules.
Fill immediately in the waiting jam jars, put on the screwtop & turn upside down.