Burgers with Mozzarella and Spinach-Arugula Pesto
|8||ounces baby spinach leaves (about 10 cups packed)|
|2||garlic cloves, peeled|
|1/2||teaspoon (packed) finely grated lemon peel|
|large pinch of dried crushed red pepper|
|4||cups (packed) fresh arugula leaves, divided (about 5 ounces)|
|3||tablespoons pine nuts|
|1||teaspoon fresh lemon juice|
|1/3||cup extra virgin olive oil|
|3||tablespoons (packed) freshly grated Parmesan cheese|
|1¾||pounds ground beef (20% fat)|
|1/2||teaspoon ground black pepper|
|6||hamburger buns, split horizontally|
|6||1/3 inch thick slices fresh mozzarella cheese (about 10 ounces)|
|2||large beefsteak tomatoes, cut into ¼ inch thick rounds|
- Rinse spinach; drain briefly, then place in large glass bowl.
- Microwave spinach, uncovered, on high just until wilted, 1 to 1½ minutes.
- Drain and squeeze out as mush liquid as possible.
- Combine garlic, lemon peel and crushed red pepper in processor; blend until garlic is finely chopped.
- Add spinach, 2 cups (packed) arugula, pine nuts, and lemon juice; process until coarse puree forms.
- With machine running, gradually add oil in thin stream and blend until almost smooth. Mix in cheese.
- Transfer pesto to small bowl; season with salt. (It can be made 6 hours ahead. Cover; chill)
- Combine ground beef, 1 teaspoon salt, 1/2 teaspoon black pepper and 6 tablespoons spinach-arugula pesto in large bowl; mix lightly with fingertips or for just until incorporated.
- Form meat mixture into six 3/4 inch thick patties. Place patties on platter.
- (Beef patties can be made 6 hours ahead. Cover and refrigerate.)
- Prepare barbecue (medium-high heat). Grill burgers top desired doneness, about 4 minutes per side for medium-rare. Grill buns, cut side down, just until lightly toasted, about 1 minute.
- Build burgers with pesto, patties, mozzarella, cheese, tomatoes and arugula.
- Cover with bun tops.