Material Angular Accordion header/title height

You dont have to use ::ng-deep. You can use [collapsedHeight] and [expandedHeight] on your mat-expansion-panel-header.

<mat-accordion [displayMode]="displayMode" [multi]="multi" class="mat-expansion-demo-width">
    <mat-expansion-panel #panel1 [hideToggle]="hideToggle">
        <mat-expansion-panel-header [collapsedHeight]="'190px'" [expandedHeight]="'190px'">
            Section 1
        </mat-expansion-panel-header>
        <p>This is the content text that makes sense here.</p>
    </mat-expansion-panel>
</mat-accordion>

Link to StackBlitz Demo.