it's well known that the limited lawmaking power that a judiciary has comes from interpretation of statutes but are there any systems where the judiciary and the legislature are one and the same and have broad lawmaking powers ?
Historically, this was true in the Icelandic Commonwealth in the Middle Ages, and in some democratic Greek city-states in the classical era.
Similarly, in non-democratic feudal regimes, the lord or monarch was both the law giver and sitting in court was also the arbiter of all disputes arising under the lord's own laws. In places like Saudi Arabia where the monarchy's power is more than symbolic, the system still works this way to a significant extent. The practical reality in most one party Communist states is similar.
In the United Kingdom, historically, the Appellate committee of the House of Lords (staffed by a subset of aristocrats usually appointed for life by the Prime Minister to the post) was the highest court of appeal of other courts in the British Commonwealth (with the Judicial committee of the Privy Council handling final appeals from outside Britain), and it was also a court of original jurisdiction for certain criminal cases against other aristocrats to satisfy the Magna Carta's notion that one is entitled to a jury of one's peers.
Top level general purpose legislatures rarely serve as courts at the highest level, except in very isolated political matters.
A good example of narrow quasi-judicial legislative power is the power of the Congress in the U.S., to be the ultimate judge for Congressional election disputes and of some Presidential election disputes. Congress also has quasi-judicial jurisdiction over impeachments of government employees whether or not they are elected, and over expulsions for cause of its own members and over other ethical sanctions of its own members.
Many other legislatures have some sort of quansi-judicial impeachment and/or explusion power exercised as a whole by by some committee within it.
It is common in the United States for administrative agencies, within their narrow area of competence to exercise both quasi-legislative power to enact regulations with a broad mandate in a subject area, and also to have quasi-judicial power in that same subject area. The Securities and Exchange Commission, the National Labor Relations Board, the Internal Revenue Service, the Environmental Protection Agency, and the Merit System Protection Board, for example, all operate in this fashion to some extent.
Likewise, it is very common at the local government level for a city council and its planning board to carry out both legislative roles and quasi-judicial role when disputes come up regarding its land use regulations.
Similarly, school boards routinely both establish employment regulations and other school rules, and serve in a quasi-judicial role with respect employee discipline or termination, and with respect to student discipline. This dual role is also common for the boards of other public institutions like hospitals and state colleges, and for private non-profit organizations.
A recent example in that kind of situation is Colorado's State School Board which both exercises legislative power over when charter schools (i.e. public schools not under the direct supervision of any elected local school board) may be formed, and has the ultimate and final judicial review role over decisions by local school boards to grant or deny school charters.