Yeah, boost the sunlight I’m actually not kidding, if you use HDRI’s to light your scene, the sun will usually be pretty bright (like, above full white), but not have the actual luminance value. Like, 3 stops are per definition HDR, but you would need a lot more to capture the full brightness. Either edit the HDR or add another lightsource/sun - a point light needs to be far away to cast relatively parallel shadows, a sun light may be hard to position. There are ways to scale the image, but it’s kind of advanced and I’ve seen no approach that cover all HDRI’s.
If looking for a glare effect from bright highlights, you have to do it in post.
You may consider more glossy shaders. Diffuse and rough gloss combo (and very low facing gloss, like, max 4%) should be the base porselain (gloss still white - practically all dielectrics have white gloss in combination with diffuse color, and same amount of bump but I sometimes use less bumps for gloss here). Then mix in another gloss for glazing effect, also controlled with a fresnel like effect, but with sharper highlights. You may want a small amount of bump to shine through here, and/or add low frequency sharp’ish (I always end up in trouble with this one) bump to show some unevenness. This glazing layer could have facing reflections somewhat higher.