Goat cheese and beetroot is the goat cheese sandwich with one variable changed, and that variable is earth. The base is the same bright, tart, faintly chalky soft cheese, and the question every version of this sandwich answers is what to set against its acidity. Beetroot's answer is a deep, sweet, mineral note: roasted or pickled, it brings a sugar that rounds the cheese's sharp edge and a damp, almost soil-like depth the cheese lacks entirely. The pairing works because the two halves are complementary opposites, sharp against sweet, pale against dark, dry-tart against wet-earthy, and neither dominates the other when the balance is right. It is the most common thing done to a goat cheese sandwich in Britain, and it is common because it works.
The craft is moisture control, and beetroot makes it the central problem. Cooked or pickled beetroot bleeds, freely and indelibly, so it cannot simply be laid on bread next to a soft cheese and expected to behave. The standard solution is to make the goat cheese itself the barrier: spread to the edges, it forms a fat-rich layer that the beetroot's juice cannot soak through, keeping the crumb intact and the structure from going to a pink mush. Beetroot is also wet in a way the cheese is not, so it is drained or patted and sliced thick enough to hold its place rather than slide, and the bread is plain and reasonably sturdy because it has to survive a deliberately moist filling. Pickled beetroot adds vinegar to the equation, sharpening the whole sandwich and pushing it away from sweet; roasted beetroot keeps it on the earthy-sweet side. Which one is used is the single decision that most changes the result.
This is one named member of the goat cheese family, the one whose variable is a staining, earthy-sweet root, and its own near variants are codified by how the beetroot is treated. Pickled beetroot against the tang reads sharp and clean; roasted beetroot reads deep and sweet; the addition of a few walnuts pulls the texture toward crunch and the flavour toward bitter. The plain goat cheese sandwich and the red onion version are separate builds with separate balances. Those deserve their own articles rather than being crowded in here.