This comes from the winner of the top 10 food blogs of 2012 by Saveur, Lottie and Doof, and they got it from the cookbook "Jerusalem" by Yotam Ottolenghi and Sami Tamimi". Lottie and Doof say it's the best thing they made in 2012.
Put the vinegar, onion, and dates in a small bowl. Add a pinch of salt and mix well with your hands. Leave to marinate for 20 minutes, then drain away any residual vinegar and discard.
Meanwhile, heat the butter and half of the olive oil in a medium frying pan over medium heat. Add the pita and almonds and cook for 5 to 6 minutes, stirring all of the time, until the pita is crunchy and golden brown. Remove from the heat and mix in the sumac, red pepper flakes, and 1/4 teaspoon salt. Set aside to cool.
When you are ready to serve, toss the spinach leaves with the pita mix in a large mixing bowl. Add the dates and red onion, the remaining olive oil, the lemon juice, and another pinch of salt. Taste for seasoning and serve immediately.