  We discuss plasmons of biased twisted bilayer graphene when the Fermi level
lies inside the gap. The collective excitations are a network of chiral edge
plasmons (CEP) entirely composed of excitations in the topological electronic
edge states (EES) that appear at the AB-BA interfaces. The CEP form an
hexagonal network with an unique energy scale
$\epsilon_p=\frac{e^2}{\epsilon_0\epsilon t_0}$ with $t_0$ the moir\'e lattice
constant and $\epsilon$ the dielectric constant. From the dielectric matrix we
obtain the plasmon spectra that has two main characteristics: (i) a diverging
density of states at zero energy, and (ii) the presence of a plasmonic Dirac
cone at $\hbar\omega\sim\epsilon_p/2$ with sound velocity $v_D=0.0075c$, which
is formed by zigzag and armchair current oscillations. A network model reveals
that the antisymmetry of the plasmon bands implies that CEP scatter at the
hexagon vertices maximally in the deflected chiral outgoing directions, with a
current ratio of 4/9 into each of the deflected directions and 1/9 into the
forward one. We show that scanning near-field microscopy should be able to
observe the predicted plasmonic Dirac cone and its broken symmetry phases.
