Dissolve magnesium chloride flakes in hot water, stirring until fully dissolved. Let the mixture cool to room temperature. It should have a slightly gel-like consistency.
In a double boiler or heatproof bowl over simmering water, melt the shea butter and coconut oil. Once melted, remove from heat and stir in the sweet almond oil (or jojoba oil).
Let the oil and butter mixture cool at room temperature or in the fridge until it begins to solidify but is still soft enough to whip (about 30 minutes).
Using a hand mixer or stand mixer, whip the cooled butter mixture until fluffy and creamy. Slowly add the magnesium mixture while continuing to whip. If using essential oils, add them at this stage.
Transfer the whipped magnesium body butter to an airtight jar or container. Store in a cool, dry place. The butter will keep for 3-6 months.
