In a small bowl, place yeast, 1 teaspoon sugar, and lukewarm water (this is called proofing the yeast). Allow to sit, around 10 minutes, until it becomes foamy on top.

In a large bowl or stand mixer fitted with the whisk attachment, mix together 1 1⁄2 cups flour, salt, sugar, cinnamon, ginger, nutmeg, and cloves. After the water-yeast mixture has become foamy, add to flour mixture along with oil, vanilla, and pumpkin. Mix thoroughly.

Add another cup of flour and eggs and mix until smooth. Switch to the dough hook attachment if you are using a stand mixer.

Add another 2-2 1⁄2 cups flour, mixing thoroughly and then remove from bowl and place on a floured surface. Knead remaining flour into dough, continuing to knead for around 10 minutes (or however long your hands will last).

Place dough in a greased bowl and cover with a damp towel.

Allow to rise 3-4 hours, punching down at least once if possible.

Preheat oven to 350°F. Braid challah into desired shape. Allow challah to rise another 30-60 minutes, or until you can see the size has grown and challah seems light.

In a small bowl, beat 2 egg yolks with 1 teaspoon water. In another small bowl combine the 1⁄4 cup sugar with 1 tablespoon cinnamon.

Brush egg wash liberally over challah. Sprinkle pepitas in a single layer on top of challah, followed by the cinnamon sugar and the thick sea salt if desired.

If making one large challah, bake around 27-28 minutes; if making two smaller challahs, bake 24-26 minutes.