Slice the French or Italian bread into pieces approximately 1/2 inch (1–1.25 cm) thick. Cut all the way through when making individually frozen slices, or leave the bottom connected if you prefer pull-apart sections.

In a bowl, mix the softened butter, minced or grated garlic, parsley, kosher salt, and optional Parmesan until evenly combined. Softened butter spreads more easily and stays attached to the bread better than melted butter.

Spread approximately 1 to 1 1/2 teaspoons of garlic butter over one side of each bread slice. Cover the surface evenly, paying special attention to the edges so every bite receives a little seasoned butter.

Arrange the buttered slices in a single layer on a parchment-lined baking sheet. Freeze them uncovered for 1–2 hours, or until the butter is firm and the slices no longer stick together.

Transfer the frozen slices to a freezer bag or airtight container, separating layers with parchment paper. Press out excess air, label the package with the date, and freeze for up to 2–3 months for best quality.

When ready to bake, preheat the oven to 400°F (200°C). Place the frozen slices butter-side up on a baking sheet and bake directly from frozen for 12–16 minutes.

Remove the bread when the butter is melted and the edges are lightly crisp. For a more browned surface, broil for 30–90 seconds at the end, watching closely because the bread can brown quickly.