If you don't feel like butterflying the turkey breast, opening it like a book, ask your butcher to do it for you.
Beat the eggs and season them with a pinch of salt and pepper. Pour the beaten eggs into a hot pan greased with a teaspoon of olive oil and make an omelet. Cook it on both sides – use a plate to flip it -, then slide the omelet onto a plate and let it cool down.
Place the open turkey breast on a board and season it with salt and pepper. Place the cooked ham and the fontina cheese on the turkey breast. You might want to leave an inch without stuffing on the short edges of the turkey breast, as it will be easier to roll it.
Finally, add the omelet: if it is too large, trim it and add the pieces left in the filling.
Wrap the turkey on itself, starting from the short side, pressing well as you roll it up, taking care that the filling remains well sealed inside.
Now tie the turkey breast with the butcher's twine: cut many pieces of string long enough to tie the breast on the short side, about 1 inch apart. If needed, tie the turkey breast also lengthwise, folding the turkey meat on the opposite edges as if you were tucking the blankets on a bed. Place a few sprigs of rosemary under the string, it will release its wonderful aroma while cooking.
Pour the olive oil into a pan large enough to hold the turkey breast. Be generous, depending on the size of the pot, you could use several tablespoons of olive oil.
Heat the olive oil over medium heat.
When the olive oil is hot, place the turkey into the pan. Sear the meat it over medium heat until it becomes golden brown, then turn it with two wooden spoons, so as to brown it on all four sides. It will take about ten minutes.
When the turkey breast is golden brown on each side, pour a glass of white wine over it. Let it evaporate for a few seconds, then immediately cover the pan with a lid. The moisture of the wine will cook the turkey.
Move the pot over very low heat and cook the turkey breast for about 25-30 minutes, checking towards the end to prevent it from drying too much. If you have moved the pan to a minimum, there should be no problems.
Now turn off the heat and let the turkey rest in the pan for at least an hour. Thus, the residual heat of the pan will finish to cook the turkey, leaving the meat juicy and tender. Do not skip this part, otherwise the turkey will not be cooked properly.
Now you can choose whether to serve the turkey immediately or wait until it is completely cold. If you prefer thin and nice slices, wait until the next day and stash the turkey in the refrigerator.
Once the turkey is cold, it will be much easier to slice it. To warm it, do not heat the turkey itself, which would otherwise become too dry.
Heat a serving dish and place the sliced turkey on top, then heat the cooking sauce on the pan and pour it over the turkey. This will be enough to warm it up.