Step 1

Make the meatballs: Combine all of the meatball ingredients—except the oil—in a large bowl and mix gently with your hands until just combined. Roll the mixture into golf ball-sized meatballs.

Step 2

In a large skillet, heat the oil over medium-high until it shimmers. Add the meatballs and cook, turning a few times, until browned and cooked through, about 8 minutes. Transfer to a paper towel-lined plate and let cool.

Step 3

While the meatballs cool, make the slaw: Cut the fronds off the fennel bulbs and set aside. Thinly slice the fennel bulbs (or shave on a mandoline), then toss with the reserved fronds, olive oil, vinegar, and a pinch of salt and pepper (to taste).

Step 4

Make the crispy shallots: Have a paper towel-lined plate ready. Put the vegetable oil with the shallots in a small saucepan. Turn the heat to medium and cook, stirring now and again, until they begin to turn a deep amber-brown (this should take 10 to 15 minutes). Transfer the shallots to the prepared plate, dab gently to remove some of the excess oil, and sprinkle with salt.

Step 5

Assemble the sandwiches: Toast the Potato Hot Dog Buns under the broiler in the oven until crisped and golden. Then pile a few meatballs into each bun and evenly divide the fennel slaw, crumbled feta, and crispy shallots over each. Serve warm and enjoy.