Preheat the oven to 375°F (190°C). Pat the turkey breast dry with paper towels and place it on a rimmed baking sheet or in a shallow roasting pan, skin side up.

Make herb butter

In a small bowl, combine the softened unsalted butter, olive oil, minced garlic, chopped thyme, chopped rosemary, lemon zest, kosher salt, and freshly ground black pepper. Mix thoroughly until smooth and evenly incorporated.

Season the turkey

Gently loosen the skin over the turkey breast with your fingers to create a pocket (if skin is present). Rub about half of the herb butter mixture directly under the skin over the meat, and spread the remaining butter over the skin. If using a boneless skin-on breast, ensure the underside and sides are also rubbed with a little of the mixture.

Roast

Place the prepared turkey breast in the preheated oven. Roast until the internal temperature reaches 160°F (71°C) in the thickest part of the breast (about 25–35 minutes for a 2 lb breast, but oven times vary). Start checking at 20 minutes. Rotate the pan once halfway through for even browning.

Rest

Remove the turkey from the oven when it reaches 160°F. Tent loosely with foil and let it rest for 10–15 minutes; the internal temperature will continue to rise to about 165°F (74°C) and juices will redistribute.

Slice

After resting, transfer the turkey to a cutting board. Using a sharp carving knife, slice the turkey breast crosswise into thin, even slices suitable for sandwiches (about 1/8–1/4 inch thick).

Assembly

Prepare bread and toppings

If using rolls or ciabatta, slice them in half. Lightly toast the cut sides under a broiler or in a toaster oven until just golden, about 1–2 minutes. Spread butter or mayonnaise on the cut sides while warm so it melts slightly.

Layer

Place several slices of roasted turkey onto the bottom half of each roll. Top the turkey with 1–2 slices of Havarti cheese per sandwich (depending on roll size) and a small handful of mixed greens or arugula if using. Add a spoonful of cranberry sauce or chutney if desired for a sweet-tart contrast.

Melt (optional)

For a warm, melty sandwich, place assembled open-faced sandwiches under a broiler for 1–2 minutes until the Havarti softens and begins to melt—watch closely to avoid burning.

Finish and serve

Close the sandwich with the top half of the roll. Slice in half if desired and serve immediately while the turkey is warm and the Havarti is creamy. Leftover turkey can be chilled and used within 3–4 days.