1. Prepare your ingredients. Chop the celery, onions and green bell pepper/capsicum into small even pieces and grate the garlic. Cut the chayote in half. Clean and cut the shrimp in half and cut the ham into very small cubes
2. CHAYOTE PREP: Boil water. Into a large stock pot and when the water is boiling, gently drop in the chayote halves. Cover the pot and boil for about 30 minutes, or until you can pierce with a fork, but the chayotes are still al dente. Remove the chayote halves from the water and place them on a baking sheet. Cools for about 5 minutes so the chayote can be handled
3. Scoop out the flesh, leaving about a 1/8 inch (about 3 mm thick) shell. Place the scooped out chayote flesh into a mixing bowl. When all the flesh has been removed, drain the water. Also, press the flesh to remove more excess water. Mash with a potato masher and then set aside
4. STUFFING: To a frying pan, add the butter and melt over medium low heat. When the butter is melted, add the chopped onions and sautee until translucent. Add the celery, green bell pepper/capsicum and garlic. While cooking, stir frequently to prevent scorching, for about 10 minutes.
TO FREEZE: Stuffed chayote can frozen immediately after stuffing and before baking. Wrap or place the stuffed chayote into a freezer safe airtight container. To bake, place container into the fridge overnight and then remove the chayotes and bake as directed in the instructions. Alternatively, if you have extra chayote left over after baking, either wrap or place into a freezer safe airtight container and freeze until needed. The frozen stuffed chayote will keep well for several months. Thaw overnight in the fridge and re-bake in oven until heated through.