Step 1In a big pot of liberally salted, rapidly boiling water, blanch the broccoli rabe. Cook just until it's tender but still crisp, 2 to 5 minutes, then remove from the boiling water and transfer to an ice water bath to stop the cooking. Drain and pat dry in a kitchen towel.
Step 2In a large skillet, heat the olive oil over medium-low heat. Add the garlic and the red pepper flakes and cook, gently, until the garlic toasts and crisps, about 10 minutes. Do not let the garlic burn. It's better to have it undercooked than over.
Step 3Remove the skillet from the heat and add the broccoli rabe. Season to taste with salt and lemon juice and toss in the flavored oil until lightly coated.
Step 4Transfer the broccoli rabe to a platter. (The dish can be made to this point several hours in advance and left at room temperature.)
Step 5Divide each burrata ball into 4 to 6 pieces, being careful to preserve the filling. Scatter the burrata over the top of the broccoli rabe. If there is no more olive oil in the skillet, add another tablespoon and swirl it around. Spoon the olive oil over the top of the burrata pieces and serve.