Black Bean Sweet Potato Walnut Burgers

I really enjoyed these Veg Burgers and so did my 13 year old son!!  That was unexpected.  The recipe cooks these on a BBQ but I pan fried them in my cast iron pan as I was worried about them breaking up.  The patties crisp up nicely on the outside but stay moist inside.  From Food and Drink Summer 2015.

1 large sweet potato, about 1 lb (500g)
2 tbsp olive oil
3 cloves garlic, minced
3/4 cup vegetable broth
1 1/2 cups walnut halves
1 can (540ml) black beans, drained and rinsed
1 egg
1 tsp grated lime zest
1 tsp salt
1/2 tsp freshly ground pepper
3/4 cup quick cooking rolled oats or quinoa flakes
Oil fro frying
6 soft hamburger buns, split
Guacamole
Romaine lettuce leaves
Sliced tomatoes

• Preheat oven to 375F.
• Peel sweet potato and coarsely shred on the large holes of a box grater or with a shredding blade in a food processor.  You should have about 3 cups lightly packed.
• Heat oil in a large skillet over medium high heat.  Sauté shredded sweet potato and garlic for 2 minutes or until potatoes are wilted.  Add vegetable broth and bring to a boil.  Reduce heat, cover and boil gently, stirring occasionally for about 10 minutes or until soft.  Uncover and boil for about 1 minute or until any excess liquid has evaporated.  Transfer to a large bowl and let cool completely.
• Meanwhile, spread walnuts on a baking sheet and toast for about 8 minutes or until golden and fragrant.  Transfer to a bowl and let cool completely.  Chop walnuts in a food processor until fairly finely chopped.  Transfer half to a shallow dish for coating and set aside.
• Add half of the black beans, egg, lime zest, salt and pepper to remaining walnuts in food processor and puree until smooth.  Add to bowl with sweet potatoes.  Add remaining black beans and rolled oats and stir until combined.  Cover and refrigerate for at least 1 hour, until mixture is chilled and set or for up to 12 hours.
• Shape chilled mixture into 6 equal sized patties, making them about 3/4 inch thick.  Place on a baking sheet and cover and refrigerate until cooking up to 8 hours.
• To grill, preheat BBQ to medium heat.
• Press each patty into reserved ground walnuts to lightly coat each side.
• Place patties on oiled grill.  Grill for about 4 minutes or until bottoms are browned and crisp.  Carefully flip over and grill for 3 to 4 minutes or until browned and hot in the centre.  Alternatively to fry patties, heat a thin layer of oil in a large skillet over medium heat.  Fry patties in batches, turning once for 3 to 4 minutes per side or until crisp on the outside and hot in the centre, adjusting heat and oiling pan between batches.  Meanwhile, toast cut sides of buns.
• Spread Guacamole on bottom half of buns and top with lettuce and tomato slices, then burger patty.  Top with move guacamole and replace bun tops