The flower bud can be cracked open and the seeds sprinkled on salad.
If you want an even milder flavor you can tame the pungency by immersing them in boiling salted water for 30 seconds and then plunging them into cold water to stop the cooking.
Here are some of my favorite ways to serve them:
Basil and Garlic Scape Mayonnaise
Penne with Swiss Chard and Garlic Scapes in Tarragon Cream with Walnuts
Pasta with Turnip Greens and Garlic Scapes in Lemon Cream Sauce
"Refried" Beans with Garlic Scapes
Beef Chili with Garlic Scapes and Hidden Nutrition
Garlic Scape, Parsley and Yogurt Dressing
Sauteed Garlic Scapes with Lemon and EVOO
Garlic Scape and Gruyere Biscuits
Lots of good ideas here (Serous Eats)!
More good ideas here (Food52)