Hi Manuel,
To realize the projected jumps, you simply add the flag "highest_order_dc=True" in your facet fe space, and keep the poly degree the same for both volume and facet fespace.
E.g.:
V = L2(mesh, order=4)
M = L2(mesh, order=4, highest_order_dc=True)
The global linear system with such M consists of cubic polynomials on the facet.
Take a look at section 2.2 of this reference.
www.sciencedirect.com/science/article/pii/S004578251630264X
Best,
Guosheng