Step 1

In a large saucepan, warm sour cream (just enough for butter to melt when added and allow the mixture to cool down to 120F degrees). Remove from heat and stir in 3 tablespoons butter, 5 tablespoons sugar, baking soda and salt. Cool to 120F degrees on an instant-read thermometer.

Step 2

While sour cream mixture is cooling, in a large bowl, whisk together flour and yeast. Add eggs to cooled sour cream mixture and then transfer to flour-yeast mixture.

Step 3

Mix with hands until a sticky dough forms. Turn out onto a lightly floured surface and knead lightly to form a smooth ball. (Or mix in stand mixer and knead to smooth ball.)

Step 4

Cover with an overturned bowl or greased plastic wrap and let rest 10 minutes.

Step 5

The dough will be soft. Divide in half. Working with one piece of dough at a time and using as little extra flour as possible, roll to a 1/4-inch-thick rectangle. Spread with half of the filling leaving a 1/2 border along both short side edges and top long edge un-spread (to help with sealing).

Step 6

Fold the short side edges of the dough in slightly to hold in filling and then roll from the bottom up. Lightly pinch dough along long edge to seal seam. Place seam side down on a parchment-lined sheet pan. Repeat with remaining dough and filling. Allow to rise for 1 to 1-1/2 hours, covered with greased plastic, until light and slightly puffed.

Step 7

While rising, heat oven to 350F degrees.

Step 8

Bake 35 minutes. Let cool on pan 10 minutes, then transfer from sheet pan to a cooling rack to cool completely before cutting into slices.

Step 9

Wrap leftover tightly in foil or plastic wrap.

Step 10

In a medium nonstick saucepan, mix together walnuts, milk, 1 1/2 cups sugar, 1 egg and 4 ounces butter. Bring just to a boil, reduce heat and simmer on medium-low, stirring frequently (watch and stir carefully so the filling doesn't burn), until mixture is thick.

Step 11

Cool completely before spreading on dough, but do not refrigerate or filling will become too firm to spread.

Step 12

Place poppy seeds into a food processor and process until seeds are ground, about 1 minute.

Step 13

Mix poppy seeds with 3/4 cup sugar, 1 tablespoon melted butter, lemon juice, and hot milk in a bowl; stir to combine.

Step 14

Cover poppy seed filling and refrigerate while making bread (filling will set up and thicken as it chills).