Toast the marshmallows. Line a baking sheet with parchment. Spread the marshmallows in a single layer. Broil on the top rack for 45–90 seconds, watching closely, until deep golden brown with a few darker spots. Rotate the pan if needed. They should look toasty, not burnt.

Warm the dairy. In a small saucepan, add half-and-half and milk. Heat over medium-low until steaming, not boiling. You should see wisps of steam and small bubbles at the edges.

Melt in the marshmallows. Scrape the toasted marshmallows into the warm dairy. Whisk until they dissolve and the mixture turns silky. If some bits cling, keep whisking gently over low heat for 1–2 minutes.

Add flavor and balance. Stir in sugar (start with 2 tablespoons), vanilla, and salt. Taste. Add a little more sugar if you want it sweeter. If using caramel extract or a drop or two of liquid smoke, add now. Be conservative—these are potent.

Blend for smoothness (optional but great). For a super-smooth texture, use an immersion blender for 10–15 seconds, or blend in a regular blender with the center cap vented to release steam.

Strain (optional). If you want a perfectly silky creamer, pour through a fine-mesh sieve into a clean jar. This catches any stubborn toasted bits.

Cool and store. Let the creamer cool to room temperature, then cover and refrigerate. It will thicken slightly as it chills.

Serve. Add 1–3 tablespoons to coffee or cold brew, stir, and adjust to taste. Finish with a tiny pinch of cinnamon or cocoa powder if you like.