Have you tried Jicama aka Yam Bean?

Yam Bean (Jicama) has a delicious and useful tuber that flourishes in our climate zone.  Its crisp white flesh can be used in stir-fries or as a Crudité. Always skin the root.

This plant is easy to grow and self-seeds easily if the pods are allowed to stay on the vine. Prune your bean pods and increase your crop. We don't bother and there is always plenty of yams underneath our Macadamias.

Note: Its seeds are poisonous containing rotenone so only eat the skinned tubers.

AA

Yam Bean (Jicama) has a poisonous seed and seed pod

Yam Bean vine will straggle and climb

Skinning a Yam Bean Tuber

Use Yam Bean as a Crudité. The yam can be copped into corn sized pieces and mixed with other chopped vegetables to make salad.

"Edible Portion

Only the root portion of jicama is edible. The leaves, flowers and vines of the plant contain rotenone, a natural insecticide designed to protect the plant from predators. Eating any of these parts of the plant can cause a toxic reaction. While the seed pods can sometimes be eaten when young, the mature pods are toxic. To be safe, it is best to only eat the root -- underground -- portion of the plant." 

Ref: Livestrong

"Jicama (yam bean), avocado and pineapple salad

 

2 capsicum peppers, seeded and minced; 2 tablespoons fresh lime juice; 2 tablespoons rice vinegar; 1 bunch fresh coriander, chopped fine; 1/2 teaspoon salt; 1/4 teaspoon ground black pepper; 1/4 cup olive oil; 1/2 fresh pineapple, peeled, cored, and cut into chunks; 1 jicama, peeled and sliced into strips; 3 cups lettuce or other fresh greens; 1 avocado, peeled, pitted and diced. 

Add the peppers, lime juice, rice vinegar, coriander, salt and pepper into a large bowl and mix well. Slowly drizzle in the olive oil while continually stirring. Add the pineapple and jicama and toss well so that they are coated with the dressing. Marinate for 45 minutes. 

Place the lettuce/greens into a large salad bowl and add the diced avocado over these. Add the marinated pineapple and jicama, and drizzle the remaining vinaigrette over the salad. Serve immediately." Ref: FAO

Yam Bean tubers medium (12cm width)  and small

 Skin rather than peel Yam Bean tubers. Cut the flesh into wedges to dip into your favourite dip. Grate into salads or bake with other root vegetables. Stir fry with ginger and garlic. This mild tasting vegetable will absorb other flavours and provide a crunchy texture. The tubers are easy to dig. I find Yam Bean self seeds so plant in a spot where this no concern.