Remove the lamb from the refrigerator so it comes to room temperature while you prepare the Roasted Garlic Mayo.
Place the roasted garlic cloves on a cutting board, mash with a fork and transfer to a small mixing bowl.
Add the mayonnaise, lemon juice and thyme leaves and combine until smooth. Set aside for 15 minutes to allow the flavors to develop.
Slice the sandwich rolls and spread the roasted garlic mayo on both the top and bottom of the roll. Place a layer of spinach leaves on the bottom, top with onion, tomato and lamb.
Notes
How To Make Roasted Garlic
Roasted garlic has a sweet, mellow flavor that makes it a great ingredient to include in all sorts of recipes. Here's how you make it:
Preheat the oven to 375°F. With a sharp knife, trim about 1/4-inch off the top of a head of garlic (just enough to expose the interior of each clove).
Drizzle with the olive oil and wrap loosely in aluminum foil.
Roast for 45 to 50 minutes, until the garlic is soft and sweet and set aside until cool enough to handle.
Separate the cloves of garlic and gently squeeze the bottoms until the cloves pop out of the open ends.
Storing Roasted Garlic
Roasted garlic can be made ahead and stored for up to one week. Simply place the cloves in a clean jar and cover them with olive oil. Cover the jar and refrigerate (do not store at room temperature).You can also arrange the cloves in a single layer on a plate or tray and pop them in the freezer. Once frozen they can be transferred to a zip-top freezer bag and kept for up to a month.