Break off the leaves of the escarole and wash them individually, taking care to remove any soil at the base of the stems. Shake the leaves dry, stack them up, and slice the escarole crosswise into ribbons about 1 1/2-inches wide.
Place a large deep skillet over medium heat and add the olive oil and butter. Toss in the garlic, red pepper flakes, bay leaves, and lemon slices; cook and stir for a couple of minutes, tossing to combine. Nestle the escarole into the pan and saute until it begins to wilt and shrink down, about 2 minutes. Sprinkle the escarole with a pinch of sugar and season with salt and pepper. Pour in the water and cover the pan. Simmer for 20 minutes until the escarole is tender.