Boiling of a heat transfer fluid within an electronics package, or ‘embedded immersion cooling’ as introduced herein, can potentially overcome the thermal challenges that heterogeneous integration introduces. Multiple thermal interfaces within current packages hinder the spreading of internal hot spots. The relatively low phase-change thermal resistance associated with boiling is beneficial to reduce internal hot spot temperatures and avoid other thermomechanical complications. Further, the heterogeneous integration of diverse components within package lead to differing power generation and temperature limits. Confined boiling of a working fluid contained within a package may maintain isothermalization across these components and limit thermal cross talk due to the inherent self-adjusting thermal resistance. However, the high degree of geometrical confinement significantly alters the two-phase heat dissipation characteristics. Hence, this work aims to gain a deeper understanding of the mechanistic effects of confinement on pool boiling which is crucial to understand, predict, and optimize the design of an embedded immersion cooling solution for thermal management. Experiments reveal two distinct boiling regimes for geometrically confined boiling in terms of operating heat flux, namely intermittent boiling and partial dryout. Even though the confinement reduces the dryout limit of immersion cooling, the intermittent confined boiling regime exhibits a significant enhancement in the heat transfer rate compared to that of unconfined boiling. High-speed video illustrates the bubble dynamics and provides insight into the effect of geometrical confinement on the dynamic liquid-vapor interface behavior that is attributed to the improved the heat transfer rate. Unlike vapor bubbles near the surface of unconfined pool boiling, the direction of growth and shape of the few, large confined vapor is highly chaotic.  This understanding motivates development of a stochastic tool that emphasizes both temporal and spatial chaos of confined vapor bubbles to fully harness the advantages of embedded immersion cooling for heat dissipation.