In a blender, combine egg yolks, garlic, mustard and lemon juice and puree at medium speed. Slowly add olive oil, blending until it is fully incorporated. Add salt, blend once more and set aside.
Trim off a thin slice of the root end of each romaine heart, keeping the core intact. Halve each romaine heart lengthwise.
Lay out the romaine halves, cut side up, on a rimmed baking sheet. Brush each half lightly with dressing. Place, cut side down on pre-heated grill, and cook, checking frequently, until nicely browned, about 3-5 minutes depending on how hot your grill is.
Remove from grill and place back on sheet pan. Drizzle with remaining dressing, then sprinkle generously with Gouda.
Grind black pepper over the top and serve immediately.
