Power networks have traditionally been designed to withstand credible outages, such as N-1 or N-2, often overlooking the complex interdependencies that can lead to cascading outages in modern systems. To address these evolving risks, planning models must adapt to better anticipate and mitigate cascading outages, while also guiding network expansion and the integration of advanced technologies. This paper presents a methodological framework for optimizing network expansion and battery storage investments to mitigate cascading outages. The framework uses an Optimization via Simulation (OvS) approach that incorporates detailed system failure simulations to assess the effectiveness of various network enhancements, including transmission lines, power transformers, reactive power compensation devices and battery storage units. In addition, a sampling process is used to select the number of trigger outage scenarios to be considered within the OvS approach. The effectiveness of the proposed framework is demonstrated on two test networks: a modified version of the IEEE 24-bus test network and the German transmission network. The main findings demonstrate: (a) that incorporating cascading outages into investment planning leads to different network enhancement decisions compared to conventional planning models (which exclude cascading outages), (b) that an optimal mix of network enhancements can significantly mitigate cascading outages, and (c) the computational scalability of the proposed framework.