Combine softened butter, olive oil, and minced garlic in a small bowl, stirring until the garlic distributes evenly throughout. Let this sit for 3 minutes—this resting period lets the garlic flavor infuse into the fat rather than staying sharp and raw.

Fold in fresh rosemary, parsley, lemon zest, sea salt, black pepper, and red pepper flakes with a wooden spoon. I confess I used to skip the lemon zest thinking it was extra work, until the first time I tasted the difference it made. The acidity brightens everything.

Slice your French baguette lengthwise into two long halves. This is where most home cooks hesitate—use a serrated knife and let the blade do the work instead of forcing it. One clean cut matters more than ten sawing motions.

Brush the herb butter mixture generously onto both cut sides of the baguette, making sure the garlic and herbs coat evenly. Because the mixture pools if you rush this step, spend 90 seconds here rather than 20 seconds frantically spreading.

Heat your grill to medium-high heat (around 400°F)—this is the temperature sweet spot where bread toasts without the exterior charring before the interior warms. Place the baguette halves cut-side down directly on the grates for 3 to 4 minutes until you see pronounced char marks forming.

Flip each half so the crust side faces down, then divide the mozzarella and Parmesan evenly between both pieces. I watch for the cheese to just begin melting at the edges before pulling them off—this usually takes 2 to 3 minutes depending on your grill's personality. Overcooked cheese separates and tastes greasy.

Transfer to a cutting board, slice into individual portions at a 2-inch angle, and serve immediately while the cheese still holds its shape. The beautiful grilled bread should have visible char lines and cheese that's still slightly tacky on top.